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• Problem in Building mplsh-run in lshkit

  - by Yijinsei

  Hi guy, been trying out this for quite some time but I'm still unable to built mplsh-run from lshkit Not sure if this would help to explain my situation during the building process /tmp/cc17kth4.o: In function `lshkit::MultiProbeLshRecallTable::reset(lshkit::MultiProbeLshModel, unsigned int, double, double)': mplsh-run.cpp:(.text._ZN6lshkit24MultiProbeLshRecallTable5resetENS_18MultiProbeLshModelEjdd[lshkit::MultiProbeLshRecallTable::reset(lshkit::MultiProbeLshModel, unsigned int, double, double)]+0x230): undefined reference to `lshkit::MultiProbeLshModel::recall(double) const' /tmp/cc17kth4.o: In function `void lshkit::MultiProbeLshIndex<unsigned int>::query_recall<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, float, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&) const': mplsh-run.cpp:(.text._ZNK6lshkit18MultiProbeLshIndexIjE12query_recallINS_11TopkScannerINS_6MatrixIfE8AccessorENS_6metric5l2sqrIfEEEEEEvPKffRT_[void lshkit::MultiProbeLshIndex<unsigned int>::query_recall<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, float, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&) const]+0x2c4): undefined reference to `lshkit::MultiProbeLsh::genProbeSequence(float const*, std::vector<unsigned int, std::allocator<unsigned int> >&, unsigned int) const' /tmp/cc17kth4.o: In function `void lshkit::MultiProbeLshIndex<unsigned int>::query<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, unsigned int, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&)': mplsh-run.cpp:(.text._ZN6lshkit18MultiProbeLshIndexIjE5queryINS_11TopkScannerINS_6MatrixIfE8AccessorENS_6metric5l2sqrIfEEEEEEvPKfjRT_[void lshkit::MultiProbeLshIndex<unsigned int>::query<lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> > >(float const*, unsigned int, lshkit::TopkScanner<lshkit::Matrix<float>::Accessor, lshkit::metric::l2sqr<float> >&)]+0x4a): undefined reference to `lshkit::MultiProbeLsh::genProbeSequence(float const*, std::vector<unsigned int, std::allocator<unsigned int> >&, unsigned int) const' collect2: ld returned 1 exit status the command that i used to built mplsh-run is g++ -I./lshkit/include -L/usr/lib -lm -lgsl -lgslcblas -lboost_program_options-mt mplsh-run.cpp Do you guys have any clue on how I could solve this?

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• gluLookAt alternative doesn't work

  - by Brammie

  Hey guys. I'm trying to calculate a lookat matrix myself, instead of using gluLookAt(). My problem is that my matrix doesn't work. using the same parameters on gluLookAt does work however. my way of creating a lookat matrix: Vector3 Eye, At, Up; //these should be parameters =) Vector3 zaxis = At - Eye; zaxis.Normalize(); Vector3 xaxis = Vector3::Cross(Up, zaxis); xaxis.Normalize(); Vector3 yaxis = Vector3::Cross(zaxis, xaxis); yaxis.Normalize(); float r[16] = { xaxis.x, yaxis.x, zaxis.x, 0, xaxis.y, yaxis.y, zaxis.y, 0, xaxis.z, yaxis.z, zaxis.z, 0, 0, 0, 0, 1, }; Matrix Rotation; memcpy(Rotation.values, r, sizeof(r)); float t[16] = { 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, -Eye.x, -Eye.y, -Eye.z, 1, }; Matrix Translation; memcpy(Translation.values, t, sizeof(t)); View = Rotation * Translation; // i tried reversing this as well (translation*rotation) now, when i try to use this matrix be calling glMultMatrixf, nothing shows up in my engine, while using the same eye, lookat and up values on gluLookAt works perfect as i said before. glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glMultMatrixf(View); the problem must be in somewhere in the code i posted here, i know the problem is not in my Vector3/Matrix classes, because they work fine when creating a projection matrix.

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• What does it mean to "preconcat" a matrix in Android?

  - by Brad Hein

  In reviewing: http://developer.android.com/reference/android/graphics/Canvas.html I'm wondering translate(): "preconcat the current matrix with the specified translation" -- what does this mean? I can't find a good definition of "preconcat" anywhere on the internet! The only place I can find it is in the Android Source - I'm starting to wonder if they made it up? :) I'm familiar with "concat" or concatenate, which is to append to, so what is a pre-concat?

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• Matlab wont extract first row & column because of matrix dimensions !

  - by ZaZu

  Hey guys, I am tracking an object that is thrown in air, and this object governs a parabolic pattern. Im tracking the object through a series of 30 images. I managed to exclude all the background and keep the object apparent, then used its centroid to get its coordinates and plot them. Now im supposed to predict where the object is going to fall, so I used polyfit & polyval .. the problem is, matlab says ??? Index exceeds matrix dimensions. Now the centroid creates its own structure with a row and 2 columns. Everytime the object moves in the loop, it updates the first row only .. Here is part of the code : For N=1:30 . . . x=centroid(1,1); % extract first row and column for x y=centroid(1,2); % extract secnd row and column for x plot_xy=plot(x,y) set(plot_xy,'XData',x(1:N),'YData',y(1:N)); fitting=polyfit(x(1:N),y(1:N),2); parabola=plot(x,nan(23,1)); evaluate=polyval(fitting,x); set(parabola,'YData',evaluate) . . end The error message I get is ??? Index exceeds matrix dimensions. It seems that (1:N) is causing the problems .. I honestly do not know why .. But when I remove N, the object is plotted along with its points, but polyfitting wont work, it gives me an error saying : Warning: Polynomial is not unique; degree >= number of data points. > In polyfit at 72 If I made it (1:N-1) or something, it plots more points before it starts giving me the same error (not unique ...) . Any ideas why ?? Thanks alot !!

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• Does this data structure have a name? Sort of a "linked matrix"?

  - by Bob

  Let's say I wanted similar functionality to a doubly linked list but needed a matrix instead so that each node was structured like this: public class Node { Node Up, Down, Left, Right; object Value; } Is there a name for such a structure? I've looked through this Wikipedia listing of data structures but didn't see anything similar. Unless I just missed it.

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• How can I tell if a rectangular matrix has duplicate rows in Matlab?

  - by Nathan Fellman

  I have a rectangular n x m matrix (n != m). What's the best way to find out if there are any duplicate rows in it in Matlab? What's the best way to find the indices of the duplicates?

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• Is there a better way to declare an empty, typed matrix in MATLAB?

  - by Arthur Ward

  Is there a way to "declare" a variable with a particular user-defined type in MATLAB? zeros() only works for built-in numeric types. The only solution I've come up with involves using repmat() to duplicate a dummy object zero times: arr = repmat(myClass(), [1 0]) Without declaring variables this way, any code which does "arr(end+1) = myClass()" has to include a special case for the default empty matrix which is of type double. Have I missed something a little more sensible?

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• From an interview: Removing rows and columns in an n×n matrix to maximize the sum of remaining value

  - by cseric

  Given an n×n matrix of real numbers. You are allowed to erase any number (from 0 to n) of rows and any number (from 0 to n) of columns, and after that the sum of the remaining entries is computed. Come up with an algorithm which finds out which rows and columns to erase in order to maximize that sum.

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• Matrix Multiplication with Threads: Why is it not faster?

  - by prelic

  Hey all, So I've been playing around with pthreads, specifically trying to calculate the product of two matrices. My code is extremely messy because it was just supposed to be a quick little fun project for myself, but the thread theory I used was very similar to: #include <pthread.h> #include <stdio.h> #include <stdlib.h> #define M 3 #define K 2 #define N 3 #define NUM_THREADS 10 int A [M][K] = { {1,4}, {2,5}, {3,6} }; int B [K][N] = { {8,7,6}, {5,4,3} }; int C [M][N]; struct v { int i; /* row */ int j; /* column */ }; void *runner(void *param); /* the thread */ int main(int argc, char *argv[]) { int i,j, count = 0; for(i = 0; i < M; i++) { for(j = 0; j < N; j++) { //Assign a row and column for each thread struct v *data = (struct v *) malloc(sizeof(struct v)); data->i = i; data->j = j; /* Now create the thread passing it data as a parameter */ pthread_t tid; //Thread ID pthread_attr_t attr; //Set of thread attributes //Get the default attributes pthread_attr_init(&attr); //Create the thread pthread_create(&tid,&attr,runner,data); //Make sure the parent waits for all thread to complete pthread_join(tid, NULL); count++; } } //Print out the resulting matrix for(i = 0; i < M; i++) { for(j = 0; j < N; j++) { printf("%d ", C[i][j]); } printf("\n"); } } //The thread will begin control in this function void *runner(void *param) { struct v *data = param; // the structure that holds our data int n, sum = 0; //the counter and sum //Row multiplied by column for(n = 0; n< K; n++){ sum += A[data->i][n] * B[n][data->j]; } //assign the sum to its coordinate C[data->i][data->j] = sum; //Exit the thread pthread_exit(0); } source: http://macboypro.com/blog/2009/06/29/matrix-multiplication-in-c-using-pthreads-on-linux/ For the non-threaded version, I used the same setup (3 2-d matrices, dynamically allocated structs to hold r/c), and added a timer. First trials indicated that the non-threaded version was faster. My first thought was that the dimensions were too small to notice a difference, and it was taking longer to create the threads. So I upped the dimensions to about 50x50, randomly filled, and ran it, and I'm still not seeing any performance upgrade with the threaded version. What am I missing here?

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• android spinning image

  - by user270811

  hi, i am trying to create two spinning wheels, as in pulleys, so everytime the attached rope moves, the two pulleys will rotate. i have tried two approaches: 1) use Matrix.postRotate within the onDraw() method of the View class, which calls the following: private void drawSpinningWheel(Canvas canvas) { try { canvas.save(); Bitmap bitmapOrg = null; int iDrawable = R.drawable.spinning_button; bitmapOrg = BitmapFactory.decodeResource(getResources(), iDrawable); if(bitmapOrg != null) { int width = bitmapOrg.getWidth(); int height = bitmapOrg.getHeight(); int newWidth = 24; int newHeight = 24; // calculate the scale - in this case = 0.4f float scaleWidth = ((float) newWidth) / width; float scaleHeight = ((float) newHeight) / height; // createa matrix for the manipulation Matrix matrix = new Matrix(); // resize the bit map matrix.postScale(scaleWidth, scaleHeight); matrix.postRotate((float) mDegrees++); Bitmap resizedBitmap = Bitmap.createBitmap(bitmapOrg, 0, 0, width, height, matrix, true); canvas.drawBitmap(resizedBitmap, matrix, null); } canvas.restore(); } catch(Exception e) { Log.e(TAG + "drawSpinningWheel", e.getMessage()); } } but it seems like the image not only spins but rotates around another axis 2) use SurfaceView and a separate thread, in the run() call this: private void doDraw(Canvas canvas) { // Draw the background image. Operations on the Canvas accumulate // so this is like clearing the screen. canvas.drawBitmap(mBackgroundImage, 0, 0, null); int yTop = mCanvasHeight - ((int) mY + mSpinningWheelImageHeight / 2); int xLeft = (int) mX - mSpinningWheelImageWidth / 2; ... // Draw the ship with its current rotation canvas.save(); canvas.rotate((float) mHeading++, (float) mX, mCanvasHeight - (float) mY); mSpinningWheelImage.setBounds(xLeft, yTop, xLeft + mSpinningWheelImageWidth, yTop + mSpinningWheelImageHeight); mSpinningWheelImage.draw(canvas); canvas.restore(); } i get the spinning to work but i can't add another spinning wheel. i even tried to create another thread for the second spinning wheel, only one shows up. can someone point me in the right direction? thanks.

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• Faster projected-norm (quadratic-form, metric-matrix...) style computations

  - by thekindamzkyoulike

  I need to perform lots of evaluations of the form X(:,i)' * A * X(:,i) i = 1...n where X(:,i) is a vector and A is a symmetric matrix. Ostensibly, I can either do this in a loop for i=1:n z(i) = X(:,i)' * A * X(:,i) end which is slow, or vectorise it as z = diag(X' * A * X) which wastes RAM unacceptably when X has a lot of columns. Currently I am compromising on Y = A * X for i=1:n z(i) = Y(:,i)' * X(:,i) end which is a little faster/lighter but still seems unsatisfactory. I was hoping there might be some matlab/scilab idiom or trick to achieve this result more efficiently?

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• C++ Template Classes Circular Dependency Problem

  - by TomWij

  We have two classes: template<typename T, typename Size, typename Stack, typename Sparse> class Matrix and template<typename T, typename Size> class Iterator Matrix should be able to return begin and end iterators and Iterator will keep a referrence to the Matrix to access the elements via it's interface. We don't want Iterator to depend on the internal storage of the Matrix to prevent coupling. How can we solve this cyclic dependency problem? (The internal Storage class has the same template parameters as the Matrix class and the same access procedures as the Matrix itself)

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• How can I make XOR work for logical matrix in MATLAB?

  - by Runner

  >> XOR(X,X) ??? Undefined function or method 'XOR' for input arguments of type 'logical'. Why XOR can't be used for logical matrix? And I tried a more simple example: >> A=[1 0;1 0]; >> B=[1 1;0 0]; >> XOR(A,B) ??? Undefined function or method 'XOR' for input arguments of type 'double'. How can I properly use XOR?

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• RDLC item width is dynamic and causing extra pages to be generated (image included)?

  - by Paul Mendoza

  I'm trying to format an RDLC report file in Visual Studio 2008 and I am having a formatting issue. I have a list at the bottom that contains a matrix that expands horizontally to the right. That pink box is just to visualize the problem I'm having. When the report is rendered the matrix expands and instead of filling the pink box with the matrix is pushes the space in the pink box to the right resulting in an extra page when printing the reports. One solution would be to shrink the pink box to be the size of the matrix which I've done. But then when the matrix grows the fields at the top of the report get pushed to the right by the same amount as the growth of the matrix. Can someone please let me know what they think the solution would be? Thank you!

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• how to pass arguments into function within a function in r

  - by jon

  I am writing function that involve other function from base R with alot of arguments. For example (real function is much longer): myfunction <- function (dataframe, Colv = NA) { matrix <- as.matrix (dataframe) out <- heatmap(matrix, Colv = Colv) return(out) } data(mtcars) myfunction (mtcars, Colv = NA) The heatmap has many arguments that can be passed to: heatmap(x, Rowv=NULL, Colv=if(symm)"Rowv" else NULL, distfun = dist, hclustfun = hclust, reorderfun = function(d,w) reorder(d,w), add.expr, symm = FALSE, revC = identical(Colv, "Rowv"), scale=c("row", "column", "none"), na.rm = TRUE, margins = c(5, 5), ColSideColors, RowSideColors, cexRow = 0.2 + 1/log10(nr), cexCol = 0.2 + 1/log10(nc), labRow = NULL, labCol = NULL, main = NULL, xlab = NULL, ylab = NULL, keep.dendro = FALSE, verbose = getOption("verbose"), ...) I want to use these arguments without listing them inside myfun. myfunction (mtcars, Colv = NA, col = topo.colors(16)) Error in myfunction(mtcars, Colv = NA, col = topo.colors(16)) : unused argument(s) (col = topo.colors(16)) I tried the following but do not work: myfunction <- function (dataframe, Colv = NA) { matrix <- as.matrix (dataframe) out <- heatmap(matrix, Colv = Colv, ....) return(out) } data(mtcars) myfunction (mtcars, Colv = NA, col = topo.colors(16))

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• C++ boost ublas + units dimension constraints

  - by aaa

  hello. I am seeking advice on design/general idea on how to force matrix dimension constraints on ublas matrix/vector possibly using boost units. For example, let matrix A have dimensions of time x force (for example) // does not have dimensions, time x force and force x time are not distinguished. matrix<double> A; //something like? dimension<time, force, matrix<double> > A; dimension<force, time, matrix<double> > B = trans(A); have you done something like this or do you have some good idea about how to organize such constraints? Thank you

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• How to read and save data from text file with variable number of columns in a Matrix in Matlab

  - by khan

  I have a text file with integer values. each row contains information about specific object. But unfortunately each row has different number of column. because of which when i try to use file_content = load('txtfile.txt'); it gives me error message that previous number of columns does not match. i also tried to use fgetl, fscanf, etc function but was unsuccessful. Can anybody give me a piece of code, or help me how to read a txt file and save in matrix in matlab. Three sample rows are given below. 1 1 1 1 1 95 17 54 111 92 17 54 111 92 17 54 111 92 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 54 109 92 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 58 109 96 15 58 109 96 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 58 109 96 15 56 109 94 15 56 109 94 15 58 109 96 15 58 109 96 15 56 109 94 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 17 58 111 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 56 109 94 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 1 1 1 2 96 185 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 15 56 109 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 54 107 92 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 13 56 107 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 54 109 92 15 54 109 92 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 1 1 1 3 186 245 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 56 109 94 15 58 109 96 15 58 109 96 15 58 109 96 15 58 109 96 13 58 107 96 13 56 107 94 13 56 107 94 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 56 107 94 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 58 107 96 13 60 107 98 13 58 107 96 13 58 107 96 15 58 109 96 13 58 107 96 As you can see the rows doesn't have equal number of columns. So how can i read and save it in a Matrix. Any help in this regards will be highly appreciated. Thanks

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• R matrix handling expressions aren't evaluated in a function or a "for" loop - Column extract doesn't seem to work

  - by Sal Leggio

  I have an R matrix named ddd. When I enter this, everything works fine: i <- 1 shapiro.test(ddd[,y]) ad.test(ddd[,y]) stem(ddd[,y]) print(y) The calls to Shapiro Wilk, Anderson Darling, and stem all work, and extract the same column. If I put this code in a "for" loop, the calls to Shapiro Wilk, and Anderson Darling stop working, while the the stem & leaf call and the print call continue to work. for (y in 7:10) { shapiro.test(ddd[,y]) ad.test(ddd[,y]) stem(ddd[,y]) print(y) } The decimal point is 1 digit(s) to the right of the | 0 | 0 0 | 899999 1 | 0 [1] 7 The same thing happens if I try and write a function. SW & AD do not work. The other calls do. D <- function (y) { + shapiro.test(ddd[,y]) + ad.test(ddd[,y]) + stem(ddd[,y]) + print(y) } D(9) The decimal point is at the | 9 | 000 9 | 10 | 00000 [1] 9 Why don't all the calls behave the same way?

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• Scala : reference is ambiguous (imported twice)

  - by tk

  I want to use a method as a parameter of another method of the same class. I have a class and objects which are companions: class mM(var elem:Matrix){ //apply a function on a dimension rows (1) or cols (2) def app(func:Iterable[Double]=>Double)(dim : Int) : Matrix = { ... } //utility function def logsumexp(): Double = {...} } object mM{ def apply(elem:Matrix):mM={new mM(elem)} def logsumexp(elem:Iterable[Double]): Double ={ this.apply(elem.asInstanceOf[Matrix]).logsumexp() } } Normally I use logsumexp like this mM(matrix).logsumexp but if want to apply it to the rows I can't use mM(matrix).app(mM.logsumexp)(1), I get the error: error: reference to mM is ambiguous; it is imported twice in the same scope by import mM and import mM What is the most elegant solution ? Should I change logsumexp() to another class ? Thanks,=)

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• Confusion over C++ new operator and classes

  - by Nils

  Hi all I created a simple class in C++ which has a private dynamic array. In the constructor I initialize the array using new and in the destructor I free it using delete. When I instantiate the class using Class a = Class(..); it works as expected, however it seems I cannot instantiate it using the new operator (Like Class *a = new Class(..);), I always get a segmentation fault. What I don't understand is when I should use new to instantiate a class and when just call the constructor or should it be possible to instantiate a class either with new or by just calling the constructor. float** A = new float*[3]; for (int i=0; i<3; i++) { A[i] = new float[3]; } A[0][0] = 3; A[0][1] = 3; A[0][2] = 4; A[1][0] = 5; A[1][1] = 6; A[1][2] = 7; A[2][0] = 1; A[2][1] = 2; A[2][2] = 3; Matrix *M = new Matrix(A, 3, 3); delete[] A; delete M; Below the class definition.. class Matrix { private: int width; int height; int stride; float* elements; public: Matrix(float** a, int n, int m); ~Matrix(); }; Matrix::Matrix(float** a, int n, int m) { // n: num rows // m: elem per rows elements = new float[n*m]; for (int i=0; i<n; i++) { for (int j=0; j<m; j++) { elements[i*n + j] = a[n][m]; } } } Matrix::~Matrix() { delete[] elements; }

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• How do I transform a single colmn list to item matrix in R?

  - by Indy

  I currently have data that is in the following format (note, this is 1 column, 4 row matrix): aa|bb bb|cc|ee|ee cc cc|ee and I want it displayed so that the column names are: aa, bb, cc, dd, and ee. And I want there to be 4 row such that each row counts the number of times each string was present in the matching row above. ie) aa bb cc dd ee 1 1 0 0 0 0 1 1 0 2 0 0 1 0 0 0 0 1 0 1 Does anyone know how to do this in R? I would post my attempt, but it is just getting ugly and complicated. Any help would be much appreciated. Thanks in advance.

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• Is there bug in the Matrix.RotateAt method for certain angles? .Net Winforms

  - by Jules

  Here's the code i'm using to rotate: Dim m As New System.Drawing.Drawing2D.Matrix Dim size = image.Size m.RotateAt(degreeAngle, New PointF(CSng(size.Width / 2), CSng(size.Height / 2))) Dim temp As New Bitmap(600, 600, Imaging.PixelFormat.Format32bppPArgb) Dim g As Graphics = Graphics.FromImage(temp) g.Transform = m g.DrawImage(image, 0, 0) (1) Disposals removed for brevity. (2) I test the code with a 200 x 200 rectangle. (3) Size 600,600 it just an arbitrary large value that I know will fit the right and bottom sides of the rotated image for testing purposes. (4) I know, with this code, the top and left edges will be clipped because I'm not transforming the orgin after the rotate. The problem only occurs at certain angles: (1) At 90, the right hand edge disappears completely. (2) At 180, the right and bottom edges are there, but very faded. (3) At 270, the bottom edge disappears completely. Is this a known bug? If I manually rotate the corners an draw the image by specifying an output rectangle, I don't get the same problem - though it is slightly slower than using RotateAt.

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• DirectX Unproject troubles

  - by pivotnig

  I have an orthographic projection and I try to unproject a point from screen space. Following are the view and projection matrices: var w2 = ScreenWidthInPixels/2; var h2 = ScreenHeightInPixels/2; view = Matrix.LookAtLH(new Vector3(0, 0, -1), new Vector3(0, 0, 0), Vector3.UnitY); proj = Matrix.OrthoOffCenterLH(-w2, w2, -h2, h2, 0.1f, 10f); Here is how I unproject a Point p, the point is given in screen pixels: var m = Vector3.Unproject(p, 0, 0, ScreenWidthInPixels, ScreenHeightInPixels, 0.1f, 10f, // znear and zfar view *proj); My code doesn't work, the matrix m contains only Nan. When I try to invert view * proj I get back a Matrix with only zeros. So I suspect my problem has something to do with the orthographic projection matrix. Here are my questions: Could the problem be caused by an underflow due to the large values in the OrthoOffCenterLH projection? What parameters do I have to pass for x,y,width,height in Unproject(...)? What significance has the minZ and maxZ parameter in Unproject(...)? Does it matter what I pass for p.Z in Unproject(...)?

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• Android OpenGL ES 2 framebuffer not working properly

  - by user16547

  I'm trying to understand how framebuffers work. In order to achieve that, I want to draw a very basic triangle to a framebuffer texture and then draw the resulting texture to a quad on the default framebuffer. However, I only get a fraction of the triangle like below. LE: The triangle's coordinates should be (1) -0.5f, -0.5f, 0 (2) 0.5f, -0.5f, 0 (3) 0, 0.5f, 0 Here's the code to render: @Override public void onDrawFrame(GL10 gl) { renderNormalStuff(); renderFramebufferTexture(); } protected void renderNormalStuff() { GLES20.glViewport(0, 0, texWidth, texHeight); GLUtils.updateProjectionMatrix(mProjectionMatrix, texWidth, texHeight); GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, fbo[0]); GLES20.glUseProgram(mProgram); GLES20.glClearColor(.5f, .5f, .5f, 1); GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT); Matrix.setIdentityM(mModelMatrix, 0); Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0); Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0); GLES20.glUniformMatrix4fv(u_MVPMatrix, 1, false, mMVPMatrix, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[0]); GLES20.glVertexAttribPointer(a_Position, 3, GLES20.GL_FLOAT, false, 12, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, vbo[1]); GLES20.glVertexAttribPointer(a_Color, 4, GLES20.GL_FLOAT, false, 16, 0); GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, ibo[0]); GLES20.glDrawElements(GLES20.GL_TRIANGLES, indexBuffer.capacity(), GLES20.GL_UNSIGNED_BYTE, 0); GLES20.glBindBuffer(GLES20.GL_ARRAY_BUFFER, 0); GLES20.glBindBuffer(GLES20.GL_ELEMENT_ARRAY_BUFFER, 0); GLES20.glUseProgram(0); } private void renderFramebufferTexture() { GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0); GLES20.glUseProgram(fboProgram); GLES20.glClearColor(.0f, .5f, .25f, 1); GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT); GLES20.glViewport(0, 0, width, height); GLUtils.updateProjectionMatrix(mProjectionMatrix, width, height); Matrix.setIdentityM(mModelMatrix, 0); Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0); Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0); GLES20.glUniformMatrix4fv(fbo_u_MVPMatrix, 1, false, mMVPMatrix, 0); //draw the texture GLES20.glActiveTexture(GLES20.GL_TEXTURE0); GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, texture[0]); GLES20.glUniform1i(fbo_u_Texture, 0); GLUtils.sendBufferData(fbo_a_Position, 3, quadPositionBuffer); GLUtils.sendBufferData(fbo_a_TexCoordinate, 2, quadTexCoordinate); GLES20.glDrawElements(GLES20.GL_TRIANGLES, quadIndexBuffer.capacity(), GLES20.GL_UNSIGNED_BYTE, quadIndexBuffer); GLES20.glUseProgram(0); }

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• Reverse horizontal and vertical for a HTML table

  - by porton

  There is a two-dimensional array describing a HTML table. Each element of the array consists of: the cell content rowspan colspan Every row of this two dimensional array corresponds to <td> cells of a <tr> of the table which my software should generate. I need to "reverse" the array (interchange vertical and horizontal direction). Insofar I considered algorithm based on this idea: make a rectangular matrix of the size of the table and store in every element of this matrix the corresponding index of the element of the above mentioned array. (Note that two elements of the matrix may be identical due rowspan/colspan.) Then I could use this matrix to calculate rowspan/colspan for the inverted table. But this idea seems bad for me. Any other algorithms? Note that I program in PHP.

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