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• How do I get confidence intervals without inverting a singular Hessian matrix?

  - by AmalieNot

  Hello. I recently posted this to reddit and it was suggested I come here, so here I am. I'm a student working on an epidemiology model in R, using maximum likelihood methods. I created my negative log likelihood function. It's sort of gross looking, but here it is: NLLdiff = function(v1, CV1, v2, CV2, st1 = (czI01 - czV01), st2 = (czI02 - czV02), st01 = czI01, st02 = czI02, tt1 = czT01, tt2 = czT02) { prob1 = (1 + v1 * CV1 * tt1)^(-1/CV1) prob2 = ( 1 + v2 * CV2 * tt2)^(-1/CV2) -(sum(dbinom(st1, st01, prob1, log = T)) + sum(dbinom(st2, st02, prob2, log = T))) } The reason the first line looks so awful is because most of the data it takes is inputted there. czI01, for example, is already declared. I did this simply so that my later calls to the function don't all have to have awful vectors in them. I then optimized for CV1, CV2, v1 and v2 using mle2 (library bbmle). That's also a bit gross looking, and looks like: ml.cz.diff = mle2 (NLLdiff, start=list(v1 = vguess, CV1 = cguess, v2 = vguess, CV2 = cguess), method="L-BFGS-B", lower = 0.0001) Now, everything works fine up until here. ml.cz.diff gives me values that I can turn into a plot that reasonably fits my data. I also have several different models, and can get AICc values to compare them. However, when I try to get confidence intervals around v1, CV1, v2 and CV2 I have problems. Basically, I get a negative bound on CV1, which is impossible as it actually represents a square number in the biological model as well as some warnings. The warnings are this: http://i.imgur.com/B3H2l.png . Is there a better way to get confidence intervals? Or, really, a way to get confidence intervals that make sense here? What I see happening is that, by coincidence, my hessian matrix is singular for some values in the optimization space. But, since I'm optimizing over 4 variables and don't have overly extensive programming knowledge, I can't come up with a good method of optimization that doesn't rely on the hessian. I have googled the problem - it suggested that my model's bad, but I'm reconstructing some work done before which suggests that my model's really not awful (the plots I make using the ml.cz.diff look like the plots of the original work). I have also read the relevant parts of the manual as well as Bolker's book Ecological Models in R. I have also tried different optimization methods, which resulted in a longer run time but the same errors. The "SANN" method didn't finish running within an hour, so I didn't wait around to see the result. tl;dr : my confidence intervals are bad, is there a relatively straightforward way to fix them in R. My vectors are: czT01 = c(5, 5, 5, 5, 5, 5, 5, 25, 25, 25, 25, 25, 25, 25, 50, 50, 50, 50, 50, 50, 50) czT02 = c(5, 5, 5, 5, 5, 10, 10, 10, 10, 10, 25, 25, 25, 25, 25, 50, 50, 50, 50, 50, 75, 75, 75, 75, 75) czI01 = c(25, 24, 22, 22, 26, 23, 25, 25, 25, 23, 25, 18, 21, 24, 22, 23, 25, 23, 25, 25, 25) czI02 = c(13, 16, 5, 18, 16, 13, 17, 22, 13, 15, 15, 22, 12, 12, 13, 13, 11, 19, 21, 13, 21, 18, 16, 15, 11) czV01 = c(1, 4, 5, 5, 2, 3, 4, 11, 8, 1, 11, 12, 10, 16, 5, 15, 18, 12, 23, 13, 22) czV02 = c(0, 3, 1, 5, 1, 6, 3, 4, 7, 12, 2, 8, 8, 5, 3, 6, 4, 6, 11, 5, 11, 1, 13, 9, 7) and I get my guesses by: v = -log((c(czI01, czI02) - c(czV01, czV02))/c(czI01, czI02))/c(czT01, czT02) vguess = mean(v) cguess = var(v)/vguess^2 It's also possible that I'm doing something else completely wrong, but my results seem reasonable so I haven't caught it.

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• How do I translate this Matlab bsxfun call to R?

  - by claytontstanley

  I would also (fingers crossed) like the solution to work with R Sparse Matrices in the Matrix package. >> A = [1,2,3,4,5] A = 1 2 3 4 5 >> B = [1;2;3;4;5] B = 1 2 3 4 5 >> bsxfun(@times, A, B) ans = 1 2 3 4 5 2 4 6 8 10 3 6 9 12 15 4 8 12 16 20 5 10 15 20 25 >> EDIT: I would like to do a matrix multiplication of these sparse vectors, and return a sparse array: > class(NRowSums) [1] "dsparseVector" attr(,"package") [1] "Matrix" > class(NColSums) [1] "dsparseVector" attr(,"package") [1] "Matrix" > NRowSums * NColSums (I think) w/o using a non-sparse variable to temporarily store data.

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• QR Code encoding and decoding using zxing

  - by helixed

  Okay, so I'm going to take the off chance that someone here has used zxing before. I'm developing a Java application, and one of the things it needs to do is encode a byte array of data into a QR Code and then decode it at a later time. Here's an example of what my encoder looks like: byte[] b = {0x48, 0x45, 0x4C, 0x4C, 0x4F}; //convert the byte array into a UTF-8 string String data; try { data = new String(b, "UTF8"); } catch (UnsupportedEncodingException e) { //the program shouldn't be able to get here return; } //get a byte matrix for the data ByteMatrix matrix; com.google.zxing.Writer writer = new QRCodeWriter(); try { matrix = writer.encode(data, com.google.zxing.BarcodeFormat.QR_CODE, width, height); } catch (com.google.zxing.WriterException e) { //exit the method return; } //generate an image from the byte matrix int width = matrix.getWidth(); int height = matrix.getHeight(); byte[][] array = matrix.getArray(); //create buffered image to draw to BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); //iterate through the matrix and draw the pixels to the image for (int y = 0; y < height; y++) { for (int x = 0; x < width; x++) { int grayValue = array[y][x] & 0xff; image.setRGB(x, y, (grayValue == 0 ? 0 : 0xFFFFFF)); } } //write the image to the output stream ImageIO.write(image, "png", outputStream); The beginning byte array in this code is just used to test it. The actual byte data will be varied. Here's what my decoder looks like: //get the data from the input stream BufferedImage image = ImageIO.read(inputStream); //convert the image to a binary bitmap source LuminanceSource source = new BufferedImageLuminanceSource(image); BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source)); //decode the barcode QRCodeReader reader = new QRCodeReader(); Result result; try { result = reader.decode(bitmap, hints); } catch (ReaderException e) { //the data is improperly formatted throw new MCCDatabaseMismatchException(); } byte[] b = result.getRawBytes(); System.out.println(ByteHelper.convertUnsignedBytesToHexString(result.getText().getBytes("UTF8"))); System.out.println(ByteHelper.convertUnsignedBytesToHexString(b)); convertUnsignedBytesToHexString(byte) is a method which converts an array of bytes in a string of hexadecimal characters. When I try to run these two blocks of code together, this is the output: 48454c4c4f 202b0b78cc00ec11ec11ec11ec11ec11ec11ec Clearly the text is being encoded, but the actual bytes of data are completely off. Any help would be appreciated here. Thanks, helixed

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• Problem installing packages

  - by gappy

  I am installing Matrix on a Linux x86_64 multicore system. I receive a message: Warning message: In install.packages("Matrix", dependencies = TRUE) : package 'Matrix' is not available Sure enough, there are not many details on package troubleshooting. It appears that Matrix is available for x86_64, but it's not available in any repository. How come?

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• How to store generated eigen faces for future face recognition?

  - by user3237134

  My code works in the following manner: 1.First, it obtains several images from the training set 2.After loading these images, we find the normalized faces,mean face and perform several calculation. 3.Next, we ask for the name of an image we want to recognize 4.We then project the input image into the eigenspace, and based on the difference from the eigenfaces we make a decision. 5.Depending on eigen weight vector for each input image we make clusters using kmeans command. Source code i tried: clear all close all clc % number of images on your training set. M=1200; %Chosen std and mean. %It can be any number that it is close to the std and mean of most of the images. um=60; ustd=32; %read and show images(bmp); S=[]; %img matrix for i=1:M str=strcat(int2str(i),'.jpg'); %concatenates two strings that form the name of the image eval('img=imread(str);'); [irow icol d]=size(img); % get the number of rows (N1) and columns (N2) temp=reshape(permute(img,[2,1,3]),[irow*icol,d]); %creates a (N1*N2)x1 matrix S=[S temp]; %X is a N1*N2xM matrix after finishing the sequence %this is our S end %Here we change the mean and std of all images. We normalize all images. %This is done to reduce the error due to lighting conditions. for i=1:size(S,2) temp=double(S(:,i)); m=mean(temp); st=std(temp); S(:,i)=(temp-m)*ustd/st+um; end %show normalized images for i=1:M str=strcat(int2str(i),'.jpg'); img=reshape(S(:,i),icol,irow); img=img'; end %mean image; m=mean(S,2); %obtains the mean of each row instead of each column tmimg=uint8(m); %converts to unsigned 8-bit integer. Values range from 0 to 255 img=reshape(tmimg,icol,irow); %takes the N1*N2x1 vector and creates a N2xN1 matrix img=img'; %creates a N1xN2 matrix by transposing the image. % Change image for manipulation dbx=[]; % A matrix for i=1:M temp=double(S(:,i)); dbx=[dbx temp]; end %Covariance matrix C=A'A, L=AA' A=dbx'; L=A*A'; % vv are the eigenvector for L % dd are the eigenvalue for both L=dbx'*dbx and C=dbx*dbx'; [vv dd]=eig(L); % Sort and eliminate those whose eigenvalue is zero v=[]; d=[]; for i=1:size(vv,2) if(dd(i,i)>1e-4) v=[v vv(:,i)]; d=[d dd(i,i)]; end end %sort, will return an ascending sequence [B index]=sort(d); ind=zeros(size(index)); dtemp=zeros(size(index)); vtemp=zeros(size(v)); len=length(index); for i=1:len dtemp(i)=B(len+1-i); ind(i)=len+1-index(i); vtemp(:,ind(i))=v(:,i); end d=dtemp; v=vtemp; %Normalization of eigenvectors for i=1:size(v,2) %access each column kk=v(:,i); temp=sqrt(sum(kk.^2)); v(:,i)=v(:,i)./temp; end %Eigenvectors of C matrix u=[]; for i=1:size(v,2) temp=sqrt(d(i)); u=[u (dbx*v(:,i))./temp]; end %Normalization of eigenvectors for i=1:size(u,2) kk=u(:,i); temp=sqrt(sum(kk.^2)); u(:,i)=u(:,i)./temp; end % show eigenfaces; for i=1:size(u,2) img=reshape(u(:,i),icol,irow); img=img'; img=histeq(img,255); end % Find the weight of each face in the training set. omega = []; for h=1:size(dbx,2) WW=[]; for i=1:size(u,2) t = u(:,i)'; WeightOfImage = dot(t,dbx(:,h)'); WW = [WW; WeightOfImage]; end omega = [omega WW]; end % Acquire new image % Note: the input image must have a bmp or jpg extension. % It should have the same size as the ones in your training set. % It should be placed on your desktop ed_min=[]; srcFiles = dir('G:\newdatabase\*.jpg'); % the folder in which ur images exists for b = 1 : length(srcFiles) filename = strcat('G:\newdatabase\',srcFiles(b).name); Imgdata = imread(filename); InputImage=Imgdata; InImage=reshape(permute((double(InputImage)),[2,1,3]),[irow*icol,1]); temp=InImage; me=mean(temp); st=std(temp); temp=(temp-me)*ustd/st+um; NormImage = temp; Difference = temp-m; p = []; aa=size(u,2); for i = 1:aa pare = dot(NormImage,u(:,i)); p = [p; pare]; end InImWeight = []; for i=1:size(u,2) t = u(:,i)'; WeightOfInputImage = dot(t,Difference'); InImWeight = [InImWeight; WeightOfInputImage]; end noe=numel(InImWeight); % Find Euclidean distance e=[]; for i=1:size(omega,2) q = omega(:,i); DiffWeight = InImWeight-q; mag = norm(DiffWeight); e = [e mag]; end ed_min=[ed_min MinimumValue]; theta=6.0e+03; %disp(e) z(b,:)=InImWeight; end IDX = kmeans(z,5); clustercount=accumarray(IDX, ones(size(IDX))); disp(clustercount); QUESTIONS: 1.It is working fine for M=50(i.e Training set contains 50 images) but not for M=1200(i.e Training set contains 1200 images).It is not showing any error.There is no output.I waited for 10 min still there is no output. I think it is going infinite loop.What is the problem?Where i was wrong? 2.Instead of running the training set everytime how eigen faces generated are stored so that stored eigen faces are used for future face recoginition for a new input image.So it reduces wastage of time.

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• Vectorization of matlab code for faster execution

  - by user3237134

  My code works in the following manner: 1.First, it obtains several images from the training set 2.After loading these images, we find the normalized faces,mean face and perform several calculation. 3.Next, we ask for the name of an image we want to recognize 4.We then project the input image into the eigenspace, and based on the difference from the eigenfaces we make a decision. 5.Depending on eigen weight vector for each input image we make clusters using kmeans command. Source code i tried: clear all close all clc % number of images on your training set. M=1200; %Chosen std and mean. %It can be any number that it is close to the std and mean of most of the images. um=60; ustd=32; %read and show images(bmp); S=[]; %img matrix for i=1:M str=strcat(int2str(i),'.jpg'); %concatenates two strings that form the name of the image eval('img=imread(str);'); [irow icol d]=size(img); % get the number of rows (N1) and columns (N2) temp=reshape(permute(img,[2,1,3]),[irow*icol,d]); %creates a (N1*N2)x1 matrix S=[S temp]; %X is a N1*N2xM matrix after finishing the sequence %this is our S end %Here we change the mean and std of all images. We normalize all images. %This is done to reduce the error due to lighting conditions. for i=1:size(S,2) temp=double(S(:,i)); m=mean(temp); st=std(temp); S(:,i)=(temp-m)*ustd/st+um; end %show normalized images for i=1:M str=strcat(int2str(i),'.jpg'); img=reshape(S(:,i),icol,irow); img=img'; end %mean image; m=mean(S,2); %obtains the mean of each row instead of each column tmimg=uint8(m); %converts to unsigned 8-bit integer. Values range from 0 to 255 img=reshape(tmimg,icol,irow); %takes the N1*N2x1 vector and creates a N2xN1 matrix img=img'; %creates a N1xN2 matrix by transposing the image. % Change image for manipulation dbx=[]; % A matrix for i=1:M temp=double(S(:,i)); dbx=[dbx temp]; end %Covariance matrix C=A'A, L=AA' A=dbx'; L=A*A'; % vv are the eigenvector for L % dd are the eigenvalue for both L=dbx'*dbx and C=dbx*dbx'; [vv dd]=eig(L); % Sort and eliminate those whose eigenvalue is zero v=[]; d=[]; for i=1:size(vv,2) if(dd(i,i)>1e-4) v=[v vv(:,i)]; d=[d dd(i,i)]; end end %sort, will return an ascending sequence [B index]=sort(d); ind=zeros(size(index)); dtemp=zeros(size(index)); vtemp=zeros(size(v)); len=length(index); for i=1:len dtemp(i)=B(len+1-i); ind(i)=len+1-index(i); vtemp(:,ind(i))=v(:,i); end d=dtemp; v=vtemp; %Normalization of eigenvectors for i=1:size(v,2) %access each column kk=v(:,i); temp=sqrt(sum(kk.^2)); v(:,i)=v(:,i)./temp; end %Eigenvectors of C matrix u=[]; for i=1:size(v,2) temp=sqrt(d(i)); u=[u (dbx*v(:,i))./temp]; end %Normalization of eigenvectors for i=1:size(u,2) kk=u(:,i); temp=sqrt(sum(kk.^2)); u(:,i)=u(:,i)./temp; end % show eigenfaces; for i=1:size(u,2) img=reshape(u(:,i),icol,irow); img=img'; img=histeq(img,255); end % Find the weight of each face in the training set. omega = []; for h=1:size(dbx,2) WW=[]; for i=1:size(u,2) t = u(:,i)'; WeightOfImage = dot(t,dbx(:,h)'); WW = [WW; WeightOfImage]; end omega = [omega WW]; end % Acquire new image % Note: the input image must have a bmp or jpg extension. % It should have the same size as the ones in your training set. % It should be placed on your desktop ed_min=[]; srcFiles = dir('G:\newdatabase\*.jpg'); % the folder in which ur images exists for b = 1 : length(srcFiles) filename = strcat('G:\newdatabase\',srcFiles(b).name); Imgdata = imread(filename); InputImage=Imgdata; InImage=reshape(permute((double(InputImage)),[2,1,3]),[irow*icol,1]); temp=InImage; me=mean(temp); st=std(temp); temp=(temp-me)*ustd/st+um; NormImage = temp; Difference = temp-m; p = []; aa=size(u,2); for i = 1:aa pare = dot(NormImage,u(:,i)); p = [p; pare]; end InImWeight = []; for i=1:size(u,2) t = u(:,i)'; WeightOfInputImage = dot(t,Difference'); InImWeight = [InImWeight; WeightOfInputImage]; end noe=numel(InImWeight); % Find Euclidean distance e=[]; for i=1:size(omega,2) q = omega(:,i); DiffWeight = InImWeight-q; mag = norm(DiffWeight); e = [e mag]; end ed_min=[ed_min MinimumValue]; theta=6.0e+03; %disp(e) z(b,:)=InImWeight; end IDX = kmeans(z,5); clustercount=accumarray(IDX, ones(size(IDX))); disp(clustercount); Running time for 50 images:Elapsed time is 103.947573 seconds. QUESTIONS: 1.It is working fine for M=50(i.e Training set contains 50 images) but not for M=1200(i.e Training set contains 1200 images).It is not showing any error.There is no output.I waited for 10 min still there is no output. I think it is going infinite loop.What is the problem?Where i was wrong?

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• My vertex shader doesn't affect texture coords or diffuse info but works for position

  - by tina nyaa

  I am new to 3D and DirectX - in the past I have only used abstractions for 2D drawing. Over the past month I've been studying really hard and I'm trying to modify and adapt some of the shaders as part of my personal 'study project'. Below I have a shader, modified from one of the Microsoft samples. I set diffuse and tex0 vertex shader outputs to zero, but my model still shows the full texture and lighting as if I hadn't changed the values from the vertex buffer. Changing the position of the model works, but nothing else. Why is this? // // Skinned Mesh Effect file // Copyright (c) 2000-2002 Microsoft Corporation. All rights reserved. // float4 lhtDir = {0.0f, 0.0f, -1.0f, 1.0f}; //light Direction float4 lightDiffuse = {0.6f, 0.6f, 0.6f, 1.0f}; // Light Diffuse float4 MaterialAmbient : MATERIALAMBIENT = {0.1f, 0.1f, 0.1f, 1.0f}; float4 MaterialDiffuse : MATERIALDIFFUSE = {0.8f, 0.8f, 0.8f, 1.0f}; // Matrix Pallette static const int MAX_MATRICES = 100; float4x3 mWorldMatrixArray[MAX_MATRICES] : WORLDMATRIXARRAY; float4x4 mViewProj : VIEWPROJECTION; /////////////////////////////////////////////////////// struct VS_INPUT { float4 Pos : POSITION; float4 BlendWeights : BLENDWEIGHT; float4 BlendIndices : BLENDINDICES; float3 Normal : NORMAL; float3 Tex0 : TEXCOORD0; }; struct VS_OUTPUT { float4 Pos : POSITION; float4 Diffuse : COLOR; float2 Tex0 : TEXCOORD0; }; float3 Diffuse(float3 Normal) { float CosTheta; // N.L Clamped CosTheta = max(0.0f, dot(Normal, lhtDir.xyz)); // propogate scalar result to vector return (CosTheta); } VS_OUTPUT VShade(VS_INPUT i, uniform int NumBones) { VS_OUTPUT o; float3 Pos = 0.0f; float3 Normal = 0.0f; float LastWeight = 0.0f; // Compensate for lack of UBYTE4 on Geforce3 int4 IndexVector = D3DCOLORtoUBYTE4(i.BlendIndices); // cast the vectors to arrays for use in the for loop below float BlendWeightsArray[4] = (float[4])i.BlendWeights; int IndexArray[4] = (int[4])IndexVector; // calculate the pos/normal using the "normal" weights // and accumulate the weights to calculate the last weight for (int iBone = 0; iBone < NumBones-1; iBone++) { LastWeight = LastWeight + BlendWeightsArray[iBone]; Pos += mul(i.Pos, mWorldMatrixArray[IndexArray[iBone]]) * BlendWeightsArray[iBone]; Normal += mul(i.Normal, mWorldMatrixArray[IndexArray[iBone]]) * BlendWeightsArray[iBone]; } LastWeight = 1.0f - LastWeight; // Now that we have the calculated weight, add in the final influence Pos += (mul(i.Pos, mWorldMatrixArray[IndexArray[NumBones-1]]) * LastWeight); Normal += (mul(i.Normal, mWorldMatrixArray[IndexArray[NumBones-1]]) * LastWeight); // transform position from world space into view and then projection space //o.Pos = mul(float4(Pos.xyz, 1.0f), mViewProj); o.Pos = mul(float4(Pos.xyz, 1.0f), mViewProj); o.Diffuse.x = 0.0f; o.Diffuse.y = 0.0f; o.Diffuse.z = 0.0f; o.Diffuse.w = 0.0f; o.Tex0 = float2(0,0); return o; } technique t0 { pass p0 { VertexShader = compile vs_3_0 VShade(4); } } I am currently using the SlimDX .NET wrapper around DirectX, but the API is extremely similar: public void Draw() { var device = vertexBuffer.Device; device.Clear(ClearFlags.Target | ClearFlags.ZBuffer, Color.White, 1.0f, 0); device.SetRenderState(RenderState.Lighting, true); device.SetRenderState(RenderState.DitherEnable, true); device.SetRenderState(RenderState.ZEnable, true); device.SetRenderState(RenderState.CullMode, Cull.Counterclockwise); device.SetRenderState(RenderState.NormalizeNormals, true); device.SetSamplerState(0, SamplerState.MagFilter, TextureFilter.Anisotropic); device.SetSamplerState(0, SamplerState.MinFilter, TextureFilter.Anisotropic); device.SetTransform(TransformState.World, Matrix.Identity * Matrix.Translation(0, -50, 0)); device.SetTransform(TransformState.View, Matrix.LookAtLH(new Vector3(-200, 0, 0), Vector3.Zero, Vector3.UnitY)); device.SetTransform(TransformState.Projection, Matrix.PerspectiveFovLH((float)Math.PI / 4, (float)device.Viewport.Width / device.Viewport.Height, 10, 10000000)); var material = new Material(); material.Ambient = material.Diffuse = material.Emissive = material.Specular = new Color4(Color.White); material.Power = 1f; device.SetStreamSource(0, vertexBuffer, 0, vertexSize); device.VertexDeclaration = vertexDeclaration; device.Indices = indexBuffer; device.Material = material; device.SetTexture(0, texture); var param = effect.GetParameter(null, "mWorldMatrixArray"); var boneWorldTransforms = bones.OrderedBones.OrderBy(x => x.Id).Select(x => x.CombinedTransformation).ToArray(); effect.SetValue(param, boneWorldTransforms); effect.SetValue(effect.GetParameter(null, "mViewProj"), Matrix.Identity);// Matrix.PerspectiveFovLH((float)Math.PI / 4, (float)device.Viewport.Width / device.Viewport.Height, 10, 10000000)); effect.SetValue(effect.GetParameter(null, "MaterialDiffuse"), material.Diffuse); effect.SetValue(effect.GetParameter(null, "MaterialAmbient"), material.Ambient); effect.Technique = effect.GetTechnique(0); var passes = effect.Begin(FX.DoNotSaveState); for (var i = 0; i < passes; i++) { effect.BeginPass(i); device.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, skin.Vertices.Length, 0, skin.Indicies.Length / 3); effect.EndPass(); } effect.End(); } Again, I set diffuse and tex0 vertex shader outputs to zero, but my model still shows the full texture and lighting as if I hadn't changed the values from the vertex buffer. Changing the position of the model works, but nothing else. Why is this? Also, whatever I set in the bone transformation matrices doesn't seem to have an effect on my model. If I set every bone transformation to a zero matrix, the model still shows up as if nothing had happened, but changing the Pos field in shader output makes the model disappear. I don't understand why I'm getting this kind of behaviour. Thank you!

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• How to reshape matrices in Mathematica

  - by speciousfool

  When manipulating matrices it is often convenient to change their shape. For instance, to turn an N x M sized matrix into a vector of length N X M. In MATLAB a reshape function exists: RESHAPE(X,M,N) returns the M-by-N matrix whose elements are taken columnwise from X. An error results if X does not have M*N elements. In the case of converting between a matrix and vector I can use the Mathematica function Flatten which takes advantage of Mathematica's nested list representation for matrices. As a quick example, suppose I have a matrix X: With Flatten[X] I can get the vector {1,2,3,...,16}. But what would be far more useful is something akin to applying Matlab's reshape(X,2,8) which would result in the following Matrix: This would allow creation of arbitrary matrices as long as the dimensions equal N*M. As far as I can tell, there isn't anything built in which makes me wonder if someone hasn't coded up a Reshape function of their own.

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• What sort of loop structure to compare checkbox matrix with Google Maps markers?

  - by Kirkman14

  I'm trying to build a map of trails around my town. I'm using an XML file to hold all the trail data. For each marker, I have categories like "surface," "difficulty," "uses," etc. I have seen many examples of Google Maps that use checkboxes to show markers by category. However these examples are usually very simple: maybe three different checkboxes. What's different on my end is that I have multiple categories, and within each category there are several possible values. So, a particular trail might have "use" values of "hiking," "biking," "jogging," and "equestrian" because all are allowed. I put together one version, which you can see here: http://www.joshrenaud.com/pd/trails_withcheckboxes3.html In this version, any trail that has any value checked by the user will be displayed on the map. This version works. (although I should point out there is a bug where despite only one category being checked on load, all markers display anyway. After your first click on any checkbox, the map will work properly) However I now realize it's not quite what I want. I want to change it so that it will display only markers that match ALL the values that are checked (rather than ANY, which is what the example above does). I took a hack at this. You can see the result online, but I can't type a link to it because I am new user. Change the "3" in the URL above to a "4" to see it. My questions are about this SECOND url. (trails_withcheckboxes4.html) It doesn't work. I am pretty new to Javascript, so I am sure I have done something totally wrong, but I can't figure out what. My specific questions: Does anyone see anything glaringly obvious that is keeping my second example from working? If not, could someone just suggest what sort of loop structure I would need to build to compare the several arrays of checkboxes with the several arrays of values on any given marker? Here is some of the relevant code, although you can just view source on the examples above to see the whole thing: function createMarker(point,surface,difficulty,use,html) { var marker = new GMarker(point,GIcon); marker.mysurface = surface; marker.mydifficulty = difficulty; marker.myuse = use; GEvent.addListener(marker, "click", function() { marker.openInfoWindowHtml(html); }); gmarkers.push(marker); return marker; } function show() { hide(); var surfaceChecked = []; var difficultyChecked = []; var useChecked = []; var j=0; // okay, let's run through the checkbox elements and make arrays to serve as holders of any values the user has checked. for (i=0; i<surfaceArray.length; i++) { if (document.getElementById('surface'+surfaceArray[i]).checked == true) { surfaceChecked[j] = surfaceArray[i]; j++; } } j=0; for (i=0; i<difficultyArray.length; i++) { if (document.getElementById('difficulty'+difficultyArray[i]).checked == true) { difficultyChecked[j] = difficultyArray[i]; j++; } } j=0; for (i=0; i<useArray.length; i++) { if (document.getElementById('use'+useArray[i]).checked == true) { useChecked[j] = useArray[i]; j++; } } //now that we have our 'xxxChecked' holders, it's time to go through all the markers and see which to show. for (var k=0; k<gmarkers.length; k++) { // this loop runs thru all markers var surfaceMatches = []; var difficultyMatches = []; var useMatches = []; var surfaceOK = false; var difficultyOK = false; var useOK = false; for (var l=0; l<surfaceChecked.length; l++) { // this loops runs through all checked Surface categories for (var m=0; m<gmarkers[k].mysurface.length; m++) { // this loops through all surfaces on the marker if (gmarkers[k].mysurface[m].childNodes[0].nodeValue == surfaceChecked[l]) { surfaceMatches[l] = true; } } } for (l=0; l<difficultyChecked.length; l++) { // this loops runs through all checked Difficulty categories for (m=0; m<gmarkers[k].mydifficulty.length; m++) { // this loops through all difficulties on the marker if (gmarkers[k].mydifficulty[m].childNodes[0].nodeValue == difficultyChecked[l]) { difficultyMatches[l] = true; } } } for (l=0; l<useChecked.length; l++) { // this loops runs through all checked Use categories for (m=0; m<gmarkers[k].myuse.length; m++) { // this loops through all uses on the marker if (gmarkers[k].myuse[m].childNodes[0].nodeValue == useChecked[l]) { useMatches[l] = true; } } } // now it's time to loop thru the Match arrays and make sure they are all completely true. for (m=0; m<surfaceMatches.length; m++) { if (surfaceMatches[m] == true) { surfaceOK = true; } else if (surfaceMatches[m] == false) {surfaceOK = false; break; } } for (m=0; m<difficultyMatches.length; m++) { if (difficultyMatches[m] == true) { difficultyOK = true; } else if (difficultyMatches[m] == false) {difficultyOK = false; break; } } for (m=0; m<useMatches.length; m++) { if (useMatches[m] == true) { useOK = true; } else if (useMatches[m] == false) {useOK = false; break; } } // And finally, if each of the three OK's is true, then let's show the marker. if ((surfaceOK == true) && (difficultyOK == true) && (useOK == true)) { gmarkers[i].show(); } } }

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• rdlc - phantom page break, what to check?

  - by Antonio Nakic Alfirevic

  I have a RDLC report which has some controls on the first page, which are inside a rectangle and which display ok. Beneath the rectangle, i have a matrix, which spans more than one page both in width and in height. I want the matrix to start rendering on the second page. If I enable "insert break before" on the matrix, there is an extra blank page before the matrix(in print layout), which is my problem. If I reduce the amount of data, so the matrix does not span more than one page in width, there is no blank page, and all is well. I checked the Page and Body sizes, they are ok. Any tips? This has been driving me crazy all day, what can I check? Thx

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• How do i create a rotation matrix given a direction vector?

  - by Neosani

  I am trying to rotate an object to face the direction it is moving in. We want it to face the normalized velocity vector.. help... pls...

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• How can I find the maximum or minimum of a multi-dimensional matrix in Matlab?

  - by Nathan Fellman

  I have a 4D array of measurements in Matlab. Each dimension represents a different parameter for the measurement. I want to find the maximum and minimum value and the index (i.e. which parameter) of each. What's the best way to do it? I figure I can take the max of the max of the max in each dimension, but that seems like a kludge.

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• How to control an OpenGL projection matrix with iPhone accelerometer/compass values?

  - by Geri

  Is there any ready made class/formula somewhere I can use it for control my viewpoint by accelerometer's/compass's XYZ? I want to achieve the same view control like acrossair uses. I have the parts (OpenGL space, filtered accel-, compass values, and a cubic panoramic view mapped to a cube around my origin). Can somebody suggest me where to start at least?

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• FileReference and HttpService Browse Image Modify it then Upload it

  - by user177787

  Hello, I am trying to do an image uploader, user can: - browse local file with button.browse - select one and save it as a FileReference. - then we do FileReference.load() then bind the data to our image control. - after we make a rotation on it and change the data of image. - and to finish we upload it to a server. To change the data of image i get the matrix of the displayed image and transform it then i re-use the new matrix and bind it to my old image: private function TurnImage():void { //Turn it var m:Matrix = _img.transform.matrix; rotateImage(m); _img.transform.matrix = m; } Now the mater is that i really don't know how to send the data as a file to my server cause its not stored in the FileReference and data inside FileReference is readOnly so we can't change it or create a new, so i can't use .upload();. Then i tried HttpService.send but i can't figure out how you send a file and not a mxml.

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• Beagleboard: How do I send/receive data to/from the DSP?

  - by snakile

  I have a beagleboard with TMS320C64x+ DSP. I'm working on an image processing beagleboard application. Here's how it's going to work: The ARM reads an image from a file and put the image in a 2D array. The arm sends the matrix to the DSP. The DSP receives the matrix. The DSP performs the image processing algorithm on the received matrix (the algorithm code uses about 5MB of dynamically allocated memory). The DSP sends the processed image (matrix) to the ARM. The arm received the matrix. The arm saved the processed image to a file. I'v already written the code for steps 1,3,5. What is the easiest way to do steps 3+4 (sending the data)? Code examples are welcome.

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• Simple XNA 2D demo: why is my F# version slower than C# version?

  - by Den

  When running this XNA application it should display a rotated rectangle that moves from top-left corner to bottom-right corner. It looks like my F# version is noticeably much slower. It seems that the Draw method skips a lot of frames. I am using VS 2012 RC, XNA 4.0, .NET 4.5, F# 3.0. I am trying to make it as functional as possible. What could be the reason for poor performance? C#: class Program { static void Main(string[] args) { using (var game = new FlockGame()) { game.Run(); } } } public class FlockGame : Game { private GraphicsDeviceManager graphics; private DrawingManager drawingManager; private Vector2 position = Vector2.Zero; public FlockGame() { graphics = new GraphicsDeviceManager(this); } protected override void Initialize() { drawingManager = new DrawingManager(graphics.GraphicsDevice); this.IsFixedTimeStep = false; } protected override void Update(GameTime gameTime) { position = new Vector2(position.X + 50.1f * (float)gameTime.ElapsedGameTime.TotalSeconds, position.Y + 50.1f * (float)gameTime.ElapsedGameTime.TotalSeconds); base.Update(gameTime); } protected override void Draw(GameTime gameTime) { //this.GraphicsDevice.Clear(Color.Lavender) drawingManager.DrawRectangle(position, new Vector2(100.0f, 100.0f), 0.7845f, Color.Red); base.Draw(gameTime); } } public class DrawingManager { private GraphicsDevice GraphicsDevice; private Effect Effect; public DrawingManager(GraphicsDevice graphicsDevice) { GraphicsDevice = graphicsDevice; this.Effect = new BasicEffect(this.GraphicsDevice) { VertexColorEnabled = true, Projection = Matrix.CreateOrthographicOffCenter(0.0f, this.GraphicsDevice.Viewport.Width, this.GraphicsDevice.Viewport.Height, 0.0f, 0.0f, 1.0f) }; } private VertexPositionColor[] GetRectangleVertices (Vector2 center, Vector2 size, float radians, Color color) { var halfSize = size/2.0f; var topLeft = -halfSize; var bottomRight = halfSize; var topRight = new Vector2(bottomRight.X, topLeft.Y); var bottomLeft = new Vector2(topLeft.X, bottomRight.Y); topLeft = Vector2.Transform(topLeft, Matrix.CreateRotationZ(radians)) + center; topRight = Vector2.Transform(topRight, Matrix.CreateRotationZ(radians)) + center; bottomRight = Vector2.Transform(bottomRight, Matrix.CreateRotationZ(radians)) + center; bottomLeft = Vector2.Transform(bottomLeft, Matrix.CreateRotationZ(radians)) + center; return new VertexPositionColor[] { new VertexPositionColor(new Vector3(topLeft, 0.0f), color), new VertexPositionColor(new Vector3(topRight, 0.0f), color), new VertexPositionColor(new Vector3(topRight, 0.0f), color), new VertexPositionColor(new Vector3(bottomRight, 0.0f), color), new VertexPositionColor(new Vector3(bottomRight, 0.0f), color), new VertexPositionColor(new Vector3(bottomLeft, 0.0f), color), new VertexPositionColor(new Vector3(bottomLeft, 0.0f), color), new VertexPositionColor(new Vector3(topLeft, 0.0f), color) }; } public void DrawRectangle(Vector2 center, Vector2 size, float radians, Color color) { var vertices = GetRectangleVertices(center, size, radians, color); foreach (var pass in this.Effect.CurrentTechnique.Passes) { pass.Apply(); this.GraphicsDevice.DrawUserPrimitives(PrimitiveType.LineList, vertices, 0, vertices.Length/2); } } } F#: namespace Flocking module FlockingProgram = open System open Flocking [<STAThread>] [<EntryPoint>] let Main _ = use g = new FlockGame() g.Run() 0 //------------------------------------------------------------------------------ namespace Flocking open System open System.Diagnostics open Microsoft.Xna.Framework open Microsoft.Xna.Framework.Graphics open Microsoft.Xna.Framework.Input type public FlockGame() as this = inherit Game() let mutable graphics = new GraphicsDeviceManager(this) let mutable drawingManager = null let mutable position = Vector2.Zero override Game.LoadContent() = drawingManager <- new Rendering.DrawingManager(graphics.GraphicsDevice) this.IsFixedTimeStep <- false override Game.Update gameTime = position <- Vector2(position.X + 50.1f * float32 gameTime.ElapsedGameTime.TotalSeconds, position.Y + 50.1f * float32 gameTime.ElapsedGameTime.TotalSeconds) base.Update gameTime override Game.Draw gameTime = //this.GraphicsDevice.Clear(Color.Lavender) Rendering.DrawRectangle(drawingManager, position, Vector2(100.0f, 100.0f), 0.7845f, Color.Red) base.Draw gameTime //------------------------------------------------------------------------------ namespace Flocking open System open System.Collections.Generic open Microsoft.Xna.Framework open Microsoft.Xna.Framework.Graphics open Microsoft.Xna.Framework.Input module Rendering = [<AllowNullLiteral>] type DrawingManager (graphicsDevice : GraphicsDevice) = member this.GraphicsDevice = graphicsDevice member this.Effect = new BasicEffect(this.GraphicsDevice, VertexColorEnabled = true, Projection = Matrix.CreateOrthographicOffCenter(0.0f, float32 this.GraphicsDevice.Viewport.Width, float32 this.GraphicsDevice.Viewport.Height, 0.0f, 0.0f, 1.0f)) let private GetRectangleVertices (center:Vector2, size:Vector2, radians:float32, color:Color) = let halfSize = size / 2.0f let mutable topLeft = -halfSize let mutable bottomRight = halfSize let mutable topRight = new Vector2(bottomRight.X, topLeft.Y) let mutable bottomLeft = new Vector2(topLeft.X, bottomRight.Y) topLeft <- Vector2.Transform(topLeft, Matrix.CreateRotationZ(radians)) + center topRight <- Vector2.Transform(topRight, Matrix.CreateRotationZ(radians)) + center bottomRight <- Vector2.Transform(bottomRight, Matrix.CreateRotationZ(radians)) + center bottomLeft <- Vector2.Transform(bottomLeft, Matrix.CreateRotationZ(radians)) + center [| new VertexPositionColor(new Vector3(topLeft, 0.0f), color) new VertexPositionColor(new Vector3(topRight, 0.0f), color) new VertexPositionColor(new Vector3(topRight, 0.0f), color) new VertexPositionColor(new Vector3(bottomRight, 0.0f), color) new VertexPositionColor(new Vector3(bottomRight, 0.0f), color) new VertexPositionColor(new Vector3(bottomLeft, 0.0f), color) new VertexPositionColor(new Vector3(bottomLeft, 0.0f), color) new VertexPositionColor(new Vector3(topLeft, 0.0f), color) |] let DrawRectangle (drawingManager:DrawingManager, center:Vector2, size:Vector2, radians:float32, color:Color) = let vertices = GetRectangleVertices(center, size, radians, color) for pass in drawingManager.Effect.CurrentTechnique.Passes do pass.Apply() drawingManager.GraphicsDevice.DrawUserPrimitives(PrimitiveType.LineList, vertices, 0, vertices.Length/2)

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• Passing a 2D array to a function in C

  - by Tyler Treat

  I have, essentially, a matrix of data (lets say ints) that I would like to store in a 2D array in which the dimensions are not known until runtime (say x columns and y rows). I want to populate the array in a function, so I assume I need to do something like this: int main(int argc, char **argv) { int y = atoi(argv[1]); int x = atoi(argv[2]); int **matrix = malloc(x * sizeof(int*)); populateMatrix(matrix, y, x); return 0; } void populateMatrix(**matrix, int y, int x) { int i, j; for (i = 0; i < y; i++) { for (j = 0; j < x; j++) { matrix[i][j] = i * j; // populated with trivial data to keep it simple } } } Obviously this doesn't work, but I'm not sure how to do what I'm describing exactly.

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• How can I find the absolute maximum or minimum of a multi-dimensional matrix in Matlab?

  - by Nathan Fellman

  I have a 4D array of measurements in Matlab. Each dimension represents a different parameter for the measurement. I want to find the maximum and minimum value and the index (i.e. which parameter) of each. What's the best way to do it? I figure I can take the max of the max of the max in each dimension, but that seems like a kludge.

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• Row/column counter in 'apply' functions

  - by mortalitysequence

  What if one wants to apply a functon i.e. to each row of a matrix, but also wants to use as an argument for this function the number of that row. As an example, suppose you wanted to get the n-th root of the numbers in each row of a matrix, where n is the row number. Is there another way (using apply only) than column-binding the row numbers to the initial matrix, like this? test <- data.frame(x=c(26,21,20),y=c(34,29,28)) t(apply(cbind(as.numeric(rownames(test)),test),1,function(x) x[2:3]^(1/x[1]))) P.S. Actually if test was really a matrix : test <- matrix(c(26,21,20,34,29,28),nrow=3) , rownames(test) doesn't help :( Thank you.

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• What is the best way to store a 16 × (2^20) matrix in matlab?

  - by Peter

  I am thinking of writing the data to a file. Does anyone have an example of how to write a big amount of data to a file?

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• Simple C++ program on multidimensional arrays - Getting C2143 error among others. Not sure why?

  - by noobzilla

  Here is my simple multidimensional array program. The first error occurs where I declare the function addmatrices and then a second one where it is implemented. I am also getting an undefined variable error for bsize. What am I doing incorrectly? #include <iostream> #include <fstream> #include <string> #include <iomanip> using namespace std; //Function declarations void constmultiply (double matrixA[][4], int asize, double matrixC[][4], int bsize, double multiplier); //Pre: The address of the output file, the matrix to be multiplied by the constant, the matrix in which // the resultant values will be stored and the multiplier are passed in. //Post: The matrix is multiplied by the multiplier and the results are displayed on screen and written to the // output file. int addmatrices (double matrixA[][4], int asize, double matrixB[]4], int bsize, double matrixC[][4], int csize); //Pre: The addresses of three matrices are passed in //Post: The values in each of the two matrices are added together and put into a third matrix //Error Codes int INPUT_FILE_FAIL = 1; int UNEQUAL_MATRIX_SIZE = 2; //Constants const double multiplier = 2.5; const int rsize = 4; const int csize = 4; //Main Driver int main() { //Declare the two matrices double matrix1 [rsize][csize]; double matrix2 [rsize][csize]; double matrix3 [rsize][csize]; //Variables double temp; string filename; //Declare filestream object ifstream infile; //Ask the user for the name of the input file cout << "Please enter the name of the input file: "; cin >> filename; //Open the filestream object infile.open(filename.c_str()); //Verify that the input file opened correctly if (infile.fail()) { cout << "Input file failed to open" <<endl; exit(INPUT_FILE_FAIL); } //Begin reading in data from the first matrix for (int i = 0; i <= 3; i++)//i = row { for (int j = 0; j <= 3; j++)// j = column { infile >> temp; matrix1[i][j] = temp; } } //Begin reading in data from the second matrix for (int k = 0; k <= 3; k++)// k = row { for (int l = 0; l <= 3; l++)// l = column { infile >> temp; matrix2[k][l] = temp; } } //Notify user cout << "Input file open, reading matrices...Done!" << endl << "Read in 2 matrices..."<< endl; //Output the values read in for Matrix 1 for (int i = 0; i <= 3; i++) { for (int j = 0; j <= 3; j ++) { cout << setprecision(1) << matrix1[i][j] << setw(8); } cout << "\n"; } cout << setw(40)<< setfill('-') << "-" << endl ; //Output the values read in for Matrix 2 for (int i = 0; i <= 3; i++) { for (int j = 0; j <= 3; j ++) { cout << setfill(' ') << setprecision(2) << matrix2[i][j] << setw(8); } cout << "\n"; } cout << setw(40)<< setfill('-') << "-" << endl ; //Multiply matrix 1 by the multiplier value constmultiply (matrix1, rsize, matrix3, rsize, multiplier); //Output matrix 3 values to screen for (int i = 0; i <= 3; i++) { for (int j = 0; j <= 3; j ++) { cout << setfill(' ') << setprecision(2) << matrix3[i][j] << setw(8); } cout << "\n"; } cout << setw(40)<< setfill('-') << "-" << endl ; // //Add matrix1 and matrix2 // addmatrices (matrix1, 4, matrix2, 4, matrix3, 4); // //Finished adding. Now output matrix 3 values to screen // for (int i = 0; i <= 3; i++) // { //for (int j = 0; j <= 3; j ++) //{ // cout << setfill(' ') << setprecision(2) << matrix3[i][j] << setw(8); //} //cout << "\n"; // } // cout << setw(40)<< setfill('-') << "-" << endl ; //Close the input file infile.close(); return 0; } //Function implementation void constmultiply (double matrixA[][4], int asize, double matrixC[][4], int bsize, double multiplier) { //Loop through each row and multiply the value at that location with the multiplier for (int i = 0; i < asize; i++) { for (int j = 0; j < 4; j++) { matrixC[i][j] = matrixA[i][j] * multiplier; } } } int addmatrices (double matrixA[][4], int asize, double matrixB[]4], int bsize, double matrixC[][4], int csize) { //Remember that you can only add two matrices that have the same shape - i.e. They need to have an equal //number of rows and columns. Let's add some error checking for that: if(asize != bsize) { cout << "You are attempting to add two matrices that are not equal in shape. Program terminating!" << endl; return exit(UNEQUAL_MATRIX_SIZE); } //Confirmed that the matrices are of equal size, so begin adding elements for (int i = 0; i < asize; i++) { for (int j = 0; j < bsize; j++) { matrixC[i][j] = matrixA[i][j] + matrixB[i][j]; } } }

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• Numerically stable(ish) method of getting Y-intercept of mouse position?

  - by Fraser

  I'm trying to unproject the mouse position to get the position on the X-Z plane of a ray cast from the mouse. The camera is fully controllable by the user. Right now, the algorithm I'm using is... Unproject the mouse into the camera to get the ray: Vector3 p1 = Vector3.Unproject(new Vector3(x, y, 0), 0, 0, width, height, nearPlane, farPlane, viewProj; Vector3 p2 = Vector3.Unproject(new Vector3(x, y, 1), 0, 0, width, height, nearPlane, farPlane, viewProj); Vector3 dir = p2 - p1; dir.Normalize(); Ray ray = Ray(p1, dir); Then get the Y-intercept by using algebra: float t = -ray.Position.Y / ray.Direction.Y; Vector3 p = ray.Position + t * ray.Direction; The problem is that the projected position is "jumpy". As I make small adjustments to the mouse position, the projected point moves in strange ways. For example, if I move the mouse one pixel up, it will sometimes move the projected position down, but when I move it a second pixel, the project position will jump back to the mouse's location. The projected location is always close to where it should be, but it does not smoothly follow a moving mouse. The problem intensifies as I zoom the camera out. I believe the problem is caused by numeric instability. I can make minor improvements to this by doing some computations at double precision, and possibly abusing the fact that floating point calculations are done at 80-bit precision on x86, however before I start micro-optimizing this and getting deep into how the CLR handles floating point, I was wondering if there's an algorithmic change I can do to improve this? EDIT: A little snooping around in .NET Reflector on SlimDX.dll: public static Vector3 Unproject(Vector3 vector, float x, float y, float width, float height, float minZ, float maxZ, Matrix worldViewProjection) { Vector3 coordinate = new Vector3(); Matrix result = new Matrix(); Matrix.Invert(ref worldViewProjection, out result); coordinate.X = (float) ((((vector.X - x) / ((double) width)) * 2.0) - 1.0); coordinate.Y = (float) -((((vector.Y - y) / ((double) height)) * 2.0) - 1.0); coordinate.Z = (vector.Z - minZ) / (maxZ - minZ); TransformCoordinate(ref coordinate, ref result, out coordinate); return coordinate; } // ... public static void TransformCoordinate(ref Vector3 coordinate, ref Matrix transformation, out Vector3 result) { Vector3 vector; Vector4 vector2 = new Vector4 { X = (((coordinate.Y * transformation.M21) + (coordinate.X * transformation.M11)) + (coordinate.Z * transformation.M31)) + transformation.M41, Y = (((coordinate.Y * transformation.M22) + (coordinate.X * transformation.M12)) + (coordinate.Z * transformation.M32)) + transformation.M42, Z = (((coordinate.Y * transformation.M23) + (coordinate.X * transformation.M13)) + (coordinate.Z * transformation.M33)) + transformation.M43 }; float num = (float) (1.0 / ((((transformation.M24 * coordinate.Y) + (transformation.M14 * coordinate.X)) + (coordinate.Z * transformation.M34)) + transformation.M44)); vector2.W = num; vector.X = vector2.X * num; vector.Y = vector2.Y * num; vector.Z = vector2.Z * num; result = vector; } ...which seems to be a pretty standard method of unprojecting a point from a projection matrix, however this serves to introduce another point of possible instability. Still, I'd like to stick with the SlimDX Unproject routine rather than writing my own unless it's really necessary.

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• Memory is full with vertex buffer

  - by Christian Frantz

  I'm having a pretty strange problem that I didn't think I'd run into. I was able to store a 50x50 grid in one vertex buffer finally, in hopes of better performance. Before I had each cube have an individual vertex buffer and with 4 50x50 grids, this slowed down my game tremendously. But it still ran. With 4 50x50 grids with my new code, that's only 4 vertex buffers. With the 4 vertex buffers, I get a memory error. When I load the game with 1 grid, it takes forever to load and with my previous version, it started up right away. So I don't know if I'm storing chunks wrong or what but it stumped me -.- for (int x = 0; x < 50; x++) { for (int z = 0; z < 50; z++) { for (int y = 0; y <= map[x, z]; y++) { SetUpVertices(); SetUpIndices(); cubes.Add(new Cube(device, new Vector3(x, map[x, z] - y, z), grass)); } } } vertexBuffer = new VertexBuffer(device, typeof(VertexPositionTexture), vertices.Count(), BufferUsage.WriteOnly); vertexBuffer.SetData<VertexPositionTexture>(vertices.ToArray()); indexBuffer = new IndexBuffer(device, typeof(short), indices.Count(), BufferUsage.WriteOnly); indexBuffer.SetData(indices.ToArray()); Thats how theyre stored. The array I'm reading from is a byte array which defines the coordinates of my map. Now with my old version, I used the same loading from an array so that hasn't changed. The only difference is the one vertex buffer instead of 2500 for a 50x50 grid. cubes is just a normal list that holds all my cubes for the vertex buffer. Another thing that just came to mind would be my draw calls. If I'm setting an effect for each cube in my cube list, that's probably going to take a lot of memory. How can I avoid doing this? I need the foreach method to set my cubes to the right position foreach (Cube block in cube.cubes) { effect.VertexColorEnabled = false; effect.TextureEnabled = true; Matrix center = Matrix.CreateTranslation(new Vector3(-0.5f, -0.5f, -0.5f)); Matrix scale = Matrix.CreateScale(1f); Matrix translate = Matrix.CreateTranslation(block.cubePosition); effect.World = center * scale * translate; effect.View = cam.view; effect.Projection = cam.proj; effect.FogEnabled = false; effect.FogColor = Color.CornflowerBlue.ToVector3(); effect.FogStart = 1.0f; effect.FogEnd = 50.0f; cube.Draw(effect); noc++; }

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• Boosting my GA with Neural Networks and/or Reinforcement Learning

  - by AlexT

  As I have mentioned in previous questions I am writing a maze solving application to help me learn about more theoretical CS subjects, after some trouble I've got a Genetic Algorithm working that can evolve a set of rules (handled by boolean values) in order to find a good solution through a maze. That being said, the GA alone is okay, but I'd like to beef it up with a Neural Network, even though I have no real working knowledge of Neural Networks (no formal theoretical CS education). After doing a bit of reading on the subject I found that a Neural Network could be used to train a genome in order to improve results. Let's say I have a genome (group of genes), such as 1 0 0 1 0 1 0 1 0 1 1 1 0 0... How could I use a Neural Network (I'm assuming MLP?) to train and improve my genome? In addition to this as I know nothing about Neural Networks I've been looking into implementing some form of Reinforcement Learning, using my maze matrix (2 dimensional array), although I'm a bit stuck on what the following algorithm wants from me: (from http://people.revoledu.com/kardi/tutorial/ReinforcementLearning/Q-Learning-Algorithm.htm) 1. Set parameter , and environment reward matrix R 2. Initialize matrix Q as zero matrix 3. For each episode: * Select random initial state * Do while not reach goal state o Select one among all possible actions for the current state o Using this possible action, consider to go to the next state o Get maximum Q value of this next state based on all possible actions o Compute o Set the next state as the current state End Do End For The big problem for me is implementing a reward matrix R and what a Q matrix exactly is, and getting the Q value. I use a multi-dimensional array for my maze and enum states for every move. How would this be used in a Q-Learning algorithm? If someone could help out by explaining what I would need to do to implement the following, preferably in Java although C# would be nice too, possibly with some source code examples it'd be appreciated.

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• Trying to parse OpenCV YAML ouput with yaml-cpp

  - by Kenn Sebesta

  I've got a series of OpenCv generated YAML files and would like to parse them with yaml-cpp I'm doing okay on simple stuff, but the matrix representation is proving difficult. # Center of table tableCenter: !!opencv-matrix rows: 1 cols: 2 dt: f data: [ 240, 240] This should map into the vector 240 240 with type float. My code looks like: #include "yaml.h" #include <fstream> #include <string> struct Matrix { int x; }; void operator >> (const YAML::Node& node, Matrix& matrix) { unsigned rows; node["rows"] >> rows; } int main() { std::ifstream fin("monsters.yaml"); YAML::Parser parser(fin); YAML::Node doc; Matrix m; doc["tableCenter"] >> m; return 0; } But I get terminate called after throwing an instance of 'YAML::BadDereference' what(): yaml-cpp: error at line 0, column 0: bad dereference Abort trap I searched around for some documentation for yaml-cpp, but there doesn't seem to be any, aside from a short introductory example on parsing and emitting. Unfortunately, neither of these two help in this particular circumstance. As I understand, the !! indicate that this is a user-defined type, but I don't see with yaml-cpp how to parse that.

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