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• make a 3D spotlight cone matrix

  - by Soubok

  How to create the transformation matrix (4x4) that transforms a cylinder (of height 1 and diameter 1) into a cone that represents my spotlight (position, direction and cutoff angle) ? --edit-- In other words: how to draw the cone that represents my spotlight by drawing a cylinder through a suitable transformation matrix.

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• Trouble creating a button matrix in Interface Builder

  - by Jake

  Hi, I am trying to create a matrix of buttons in Interface Builder 3.2.1 but can not find anyway to do it. I read the question and answer posted here: http://stackoverflow.com/questions/1771835/how-to-create-a-nsmatrix-of-nsimagecell-in-interface-builder-in-10-6 But following Layout Embed Objects In, as suggested, I see only View and Scroll View as options, not Matrix. Have I missed something? Thanks.

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• Matrix "Zigzag" Reordering

  - by fbrereto

  I have an NxM matrix in Matlab that I would like to reorder in similar fashion to the way JPEG reorders its subblock pixels: (referenced from here) I would like the algorithm to be generic such that I can pass in a 2D matrix with any dimensions. I am a C++ programmer by trade and am very tempted to write an old school loop to accomplish this, but I suspect there is a better way to do it in Matlab.

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• Compact matlab matrix indexing notation

  - by AnnaR

  I've got an nxk sized matrix, containing k numbers per row. I want to use these k number as indexes to k-dimensional matrix. Is there any compact way of doing so in matlab or must I use a for-loop? This is what I want to do (in matlab-pseudo code), but in a more matlabish way. for row=1:1:n finalTable(row) = kDimensionalMatrix(indexmatrix(row, 1),... indexmatrix(row, 2),...,indexmatrix(row, k)) end

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• How can I concatenate multiple rows in a matrix

  - by Matthijs

  In Java I would like to concatenate an array (a[], fixed length) to an array of the same length, to create a matrix M[2][length of a]. This way I would like to subsequently paste more of those arrays onto the matrix. (Comparable to the Matlab vertcat function..C=[A;B]) Is this possible? Thanks

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• how plot a matrix on a wxframe?

  - by milton

  I am starting on wx, and I need to plot a matrix (like a grid) that is stored on a list of lists on wx Frame. My matrix have to values, and I would like to set different colors for each values. mymatrix=[[100,200,200,200,100,200,200,200,100,100], [200,200,100,100,100,100,200,200,100,200], [100,100,200,200,100,100,100,100,100,100], [100,200,200,100,200,100,100,200,200,200], [200,100,200,100,100,100,100,200,100,100], [100,200,200,100,200,200,100,200,100,100], [200,100,200,100,100,100,200,100,100,100], [200,200,100,200,100,200,200,200,200,200], [200,200,200,100,200,200,200,100,100,100], [100,100,100,200,200,200,100,200,200,100]] a = numpy.array(landscape_matrix) im = Image.fromarray(a) I can show it using im.show() but I need to plot it on a wx frame. All help is welcome. [email protected]

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• Projection on a plane using a 2*3 matrix

  - by leipäjuusto

  Hello, I can easily draw the projection of a 3D set of points onto the plane with normal vector (1,1,1), by using the matrix (-sqrt(3)/2 sqrt(3)/2 0) (-1/2 -1/2 1). I want to do the same thing, but for a projection onto an arbitrary plane with normal vector (a,b,c) instead of (1,1,1). How to find the matrix? Thanks in advance!

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• Translate along local axis

  - by Aaron

  I have an object with a position matrix and a rotation matrix (derived from a quaternion, but I digress). I'm able to translate this object along world-relative vectors, but I'm trying to figure out how to translate it along local-relative vectors. So if the object is tilted 45 degrees around its Z-axis the vector (1, 0, 0) would make it move to the upper right. For world-space translations I simply turn the movement vector into a matrix and multiply it by the position matrix: position_mat = translation_mat * position_mat. For local-space translations I'd think I'd have to use the rotation matrix into that formula, but I see the object spin around instead when I apply a translation over time no matter where I multiply the rotation matrix.

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• dximagetransform.matrix, absolutely position child elements not rotating in IE 8 standards mode

  - by davydka

  I've looked all over for more information on this, and would like to know why it happens. Here's the code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html> <head> </head> <body> <div style="position:absolute; top:200px; left:200px; height:200px; width:200px; border:1px solid black; filter: progid:DXImageTransform.Microsoft.Matrix(sizingMethod='auto expand', M11=0.9886188373396114, M12=-0.15044199698646263, M21=0.15044199698646263, M22=0.9886188373396114);"> <div style="position:absolute; top:10px; left:10px; border:1px solid darkblue;"> I do not rotate in IE 8. </div> </div> </body> </html> The problem is that absolutely or relatively positioned elements within a div that has been rotated using MS's dximagetransform.matrix do not inherit the transformation in IE 8. IE 6 & 7 render correctly, and I can solve the IE8 problem by triggering compatibility mode, but I'd rather not do that. Does anyone have any experience with this? I'm using css3 transform on other browsers and using dximagetransform.matrix to achieve this effect in IE. EDIT: Added the opening html tag. Problem still exists. http://i45.tinypic.com/nf4gmq.png

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• Functional way to get a matrix from text

  - by Elazar Leibovich

  I'm trying to solve some Google Code Jam problems, where an input matrix is typically given in this form: 2 3 #matrix dimensions 1 2 3 4 5 6 7 8 9 # all 3 elements in the first row 2 3 4 5 6 7 8 9 0 # each element is composed of three integers where each element of the matrix is composed of, say, three integers. So this example should be converted to #!scala Array( Array(A(1,2,3),A(4,5,6),A(7,8,9), Array(A(2,3,4),A(5,6,7),A(8,9,0), ) An imperative solution would be of the form #!python input = """2 3 1 2 3 4 5 6 7 8 9 2 3 4 5 6 7 8 9 0 """ lines = input.split('\n') print lines[0] m,n = (int(x) for x in lines[0].split()) array = [] row = [] A = [] for line in lines[1:]: for elt in line.split(): A.append(elt) if len(A)== 3: row.append(A) A = [] array.append(row) row = [] from pprint import pprint pprint(array) A functional solution I've thought of is #!scala def splitList[A](l:List[A],i:Int):List[List[A]] = { if (l.isEmpty) return List[List[A]]() val (head,tail) = l.splitAt(i) return head :: splitList(tail,i) } def readMatrix(src:Iterator[String]):Array[Array[TrafficLight]] = { val Array(x,y) = src.next.split(" +").map(_.trim.toInt) val mat = src.take(x).toList.map(_.split(" "). map(_.trim.toInt)). map(a => splitList(a.toList,3). map(b => TrafficLight(b(0),b(1),b(2)) ).toArray ).toArray return mat } But I really feel it's the wrong way to go because: I'm using the functional List structure for each line, and then convert it to an array. The whole code seems much less efficeint I find it longer less elegant and much less readable than the python solution. It is harder to which of the map functions operates on what, as they all use the same semantics. What is the right functional way to do that?

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• Precision error on matrix multiplication

  - by Wam

  Hello all, Coding a matrix multiplication in my program, I get precision errors (inaccurate results for large matrices). Here's my code. The current object has data stored in a flattened array, row after row. Other matrix B has data stored in a flattened array, column after column (so I can use pointer arithmetic). protected double[,] multiply (IMatrix B) { int columns = B.columns; int rows = Rows; int size = Columns; double[,] result = new double[rows,columns]; for (int row = 0; row < rows; row++) { for (int col = 0; col < columns; col++) { unsafe { fixed (float* ptrThis = data) fixed (float* ptrB = B.Data) { float* mePtr = ptrThis + row*rows; float* bPtr = ptrB + col*columns; double value = 0.0; for (int i = 0; i < size; i++) { value += *(mePtr++) * *(bPtr++); } result[row, col] = value; } } } } } Actually, the code is a bit more complicated : I do the multiply thing for several chunks (so instead of having i from 0 to size, I go from localStart to localStop), then sum up the resulting matrices. My problem : for a big matrix I get precision error : NUnit.Framework.AssertionException: Error at (0,1) expected: <6.4209571409444209E+18> but was: <6.4207619776304906E+18> Any idea ?

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• Optimization of a c++ matrix/bitmap class

  - by Andrew

  I am searching a 2D matrix (or bitmap) class which is flexible but also fast element access. The contents A flexible class should allow you to choose dimensions during runtime, and would look something like this (simplified): class Matrix { public: Matrix(int w, int h) : data(new int[x*y]), width(w) {} void SetElement(int x, int y, int val) { data[x+y*width] = val; } // ... private: // symbols int width; int* data; }; A faster often proposed solution using templates is (simplified): template <int W, int H> class TMatrix { TMatrix() data(new int[W*H]) {} void SetElement(int x, int y, int val) { data[x+y*W] = val; } private: int* data; }; This is faster as the width can be "inlined" in the code. The first solution does not do this. However this is not very flexible anymore, as you can't change the size anymore at runtime. So my question is: Is there a possibility to tell the compiler to generate faster code (like when using the template solution), when the size in the code is fixed and generate flexible code when its runtime dependend? I tried to achieve this by writing "const" where ever possible. I tried it with gcc and VS2005, but no success. This kind of optimization would be useful for many other similar cases.

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• Matlab matrix replacement assignment gives error

  - by Gulcan

  Hello, when i tried to update some part of a matrix, i got the following error message: ??? Assignment has fewer non-singleton rhs dimensions than non-singleton subscripts My code tries to update some values of a matrix that represent a binary image. My code is as follows: outImage(3:5,2:4,1) = max(imBinary(3:5,2:4,1)); When I delete last parameter (1), this time I get the same error. I guess there is a mismatch between dimensions but I could not get it. outImage is a new object that is created at that time (I tried to create it before, but nothing changed). What may be wrong? Thanks in advance, Gulcan

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• MATLAB matrix replacement assignment gives error

  - by Gulcan

  I tried to update some part of a matrix, I got the following error message: ??? Assignment has fewer non-singleton rhs dimensions than non-singleton subscripts My code tries to update some values of a matrix that represent a binary image. My code is as follows: outImage(3:5,2:4,1) = max(imBinary(3:5,2:4,1)); When I delete last parameter (1), this time I get the same error. I guess there is a mismatch between dimensions but I could not get it. outImage is a new object that is created at that time (I tried to create it before, but nothing changed). What may be wrong?

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• Problem sub-total Matrix with rdlc report in vb.NET

  - by Keven

  Hi everyone, I have a matrix and I need to add the money earned this year and past years. However, I must remove the money spent in past years. I must have the separate amount per year and the total of these amounts. This is what gives my matrix: Year = Fields!Year.value =formatnumber((sum(Fields!Results.Value))-(sum(iif( Fields!Year.value & Parameters!choosedYear.Value, Fields!Moneyspent.value,0))), 2) & "$" However, the subtotal gives me an error. What should I do? P.S.: I already found that the subtotal gives me an error because it's not in the scope of the rowgroup1, but is there a way to get the scope in the subtotal? or can anybody find another way to do it?

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• Efficient 4x4 matrix inverse (affine transform)

  - by Budric

  Hi, I was hoping someone can point out an efficient formula for 4x4 affine matrix transform. Currently my code uses cofactor expansion and it allocates a temporary array for each cofactor. It's easy to read, but it's slower than it should be. Note, this isn't homework and I know how to work it out manually using 4x4 co-factor expansion, it's just a pain and not really an interesting problem for me. Also I've googled and came up with a few sites that give you the formula already (http://www.euclideanspace.com/maths/algebra/matrix/functions/inverse/fourD/index.htm). However this one could probably be optimized further by pre-computing some of the products. I'm sure someone came up with the "best" formula for this at one point or another? Thanks.

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• Rotation Matrix calculates by column not by row

  - by pinnacler

  I have a class called forest and a property called fixedPositions that stores 100 points (x,y) and they are stored 250x2 (rows x columns) in MatLab. When I select 'fixedPositions', I can click scatter and it will plot the points. Now, I want to rotate the plotted points and I have a rotation matrix that will allow me to do that. The below code should work: theta = obj.heading * pi/180; apparent = [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; But it wont. I get this error. ??? Error using == mtimes Inner matrix dimensions must agree. Error in == landmarkslandmarks.get.apparentPositions at 22 apparent = [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; When I alter forest.fixedPositions to store the variables 2x250 instead of 250x2, the above code will work, but it wont plot. I'm going to be plotting fixedPositions constantly in a simulation, so I'd prefer to leave it as it, and make the rotation work instead. Any ideas? Also, fixed positions, is the position of the xy points as if you were looking straight ahead. i.e. heading = 0. heading is set to 45, meaning I want to rotate points clockwise 45 degrees. Here is my code: classdef landmarks properties fixedPositions %# positions in a fixed coordinate system. [x, y] heading = 45; %# direction in which the robot is facing end properties (Dependent) apparentPositions end methods function obj = landmarks(numberOfTrees) %# randomly generates numberOfTrees amount of x,y coordinates and set %the array or matrix (not sure which) to fixedPositions obj.fixedPositions = 100 * rand([numberOfTrees,2]) .* sign(rand([numberOfTrees,2]) - 0.5); end function obj = set.apparentPositions(obj,~) theta = obj.heading * pi/180; [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; end function apparent = get.apparentPositions(obj) %# rotate obj.positions using obj.facing to generate the output theta = obj.heading * pi/180; apparent = [cos(theta) -sin(theta) ; sin(theta) cos(theta)] * obj.fixedPositions; end end end P.S. If you change one line to this: obj.fixedPositions = 100 * rand([2,numberOfTrees]) .* sign(rand([2,numberOfTrees]) - 0.5); Everything will work fine... it just wont plot.

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• what is the best matrix determinant algorithm

  - by peril brain

  can anyone tell me which is the best algorithm to find the value of determinant of a matrix of size nXn.

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• Typesetting a large matrix in LaTeX

  - by Hooked

  I have a 3x12 matrix I'd like to input into my LaTeX (with amsmath) document but LaTeX seems to choke when the matrix gets larger then 3x10: \begin{equation} \textbf{e} = \begin{bmatrix} 1&1&1&1&0&0&0&0&-1&-1&-1&-1\\ 1&-1&0&0&1&1&-1&-1&0&0&1&-1\\ 0&0&1&-1&1&-1&1&-1&1&-1&0&0 \end{bmatrix} \end{equation} The error: Extra alignment tab has been changed to \cr. tells me that I have more & then the bmatrix environment can handle. Is there a proper way to handle this? Also it seems that the alignment for 1's and the -1's are different, is that also expected of the bmatrix?

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• Matrix xmpp for windows phone with sockets

  - by user1608857

  I am developing a chat application in windows phone. I am using Matrix XMPP library for that. It worked fine using BOSH. Matrix has released a new version for windows phone which supports sockets. I tried connecting to XMPP using the new version. I tried with both BOSH and Sockets. But it is not working. But it didn't worked for me. I have to develop the application with sockets. I included the line xmppClient.Transport=Transport.Bosh; And tried with sockets also xmppClient.Transport=Transport.Sockets;

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• Transposing a matrix

  - by ZaZu

  Hello, I want to transpose a matrix, its a very easy task but its not working with me : int testtranspose(testing *test,testing *test2){ int i,j; (*test2).colsmat2=(*test).rowsmat1; (*test2).rowsmat2=(*test).colsmat1 for(i=0;i<(*test).rowsmat1;i++){ for(j=0;j<(*test).colsmat1;j++){ ((*test2).mat[i][j])=((*test).mat[i][j]); } printf("\n"); } } I thought this is the correct method of doing it, but apparently for a matrix such as : 1 2 3 4 5 6 7 8 I get : 1 2 0 0 3 4 0 0 What is the problem ? Please help, Thanks !

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• ssrs: one static row matrix, multiple columns will not filter out nulls

  - by pbarton99

  Using a ssrs 2005 matrix client side. I want to list the multiple addresses of one person, hence one row, multiple columns. The Column field is =Fields!StreetName.Value. The data details field is =First(Fields!StreetPrefix.Value) & " " & First(Fields!StreetName.Value). The datasource has a row for each address; however, some rows will have nulls since the datasource is composed of outer joins. The column grouping works, but the first column is always empty, (first 2 rows of datasource are null) addresses appear only after the empty column. I want to filter out nulls on the matrix, but its like the filter is ignored. I have also tried having the dataset return an empty string for a null streetname and setting the filter to =Fields!StreetName.Value != ="" but no difference. What am I missing?

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• Values of Variables Matrix NumPy

  - by Max Mines

  I'm working on a program that determines if lines intersect. I'm using matrices to do this. I understand all the math concepts, but I'm new to Python and NumPy. I want to add my slope variables and yint variables to a new matrix. They are all floats. I can't seem to figure out the correct format for entering them. Here's an example: import numpy as np x = 2 y = 5 w = 9 z = 12 I understand that if I were to just be entering the raw numbers, it would look something like this: matr = np.matrix('2 5; 9 12') My goal, though, is to enter the variable names instead of the ints.

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• Building a world matrix

  - by DeadMG

  When building a world projection matrix from scale, rotate, translate matrices, then the translation matrix must be the last in the process, right? Else you'll be scaling or rotating your translations. Do scale and rotate need to go in a specific order? Right now I've got std::for_each(objects.begin(), objects.end(), [&, this](D3D93DObject* ptr) { D3DXMATRIX WVP; D3DXMATRIX translation, rotationX, rotationY, rotationZ, scale; D3DXMatrixTranslation(&translation, ptr->position.x, ptr->position.y, ptr->position.z); D3DXMatrixRotationX(&rotationX, ptr->rotation.x); D3DXMatrixRotationY(&rotationY, ptr->rotation.y); D3DXMatrixRotationZ(&rotationZ, ptr->rotation.z); D3DXMatrixScaling(&translation, ptr->scale.x, ptr->scale.y, ptr->scale.z); WVP = rotationX * rotationY * rotationZ * scale * translation * ViewProjectionMatrix; });

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• MATLAB - Index exceeds matrix dimensions

  - by Jessy

  Hi I have problem with matrix.. I have many .txt files with different number of rows but have the same number of column (1 column) e.g. s1.txt = 1234 rows s2.txt = 1200 rows s2.txt = 1100 rows I wanted to combine the three files. Since its have different rows .. when I write it to a new file I got this error = Index exceeds matrix dimensions. How I can solved this problem? .

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