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• Looking for PCA snippet/source code in C++

  - by jihchuan

  Hi, I'm currently developing a software to compare 2 images. I start with extract the image's RGB values, form a matrix of array and then attempt to compress the values using PCA, and then match/recognize it with a pre-set data to find its similarity. But I can't proceed with the PCA part. (I'm using C++, C also can) If there any library/source code/snippet for it please let me know, or if there're any recommendation on my case also very welcomed!! I'd appreciate your helps!! Thanks! JC, [email protected]

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• Out of memory error while using clusterdata in MATLAB

  - by Hossein

  Hi, I am trying to cluster a Matrix (size: 20057x2).: T = clusterdata(X,cutoff); but I get this error: ??? Error using == pdistmex Out of memory. Type HELP MEMORY for your options. Error in == pdist at 211 Y = pdistmex(X',dist,additionalArg); Error in == linkage at 139 Z = linkagemex(Y,method,pdistArg); Error in == clusterdata at 88 Z = linkage(X,linkageargs{1},pdistargs); Error in == kmeansTest at 2 T = clusterdata(X,1); can someone help me. I have 4GB of ram, but think that the problem is from somewhere else..

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• iPhone status bar orientation with opengl

  - by sfider

  I have opengl only view that displays in portrait and landscape mode using projection matrix (view's transformation is identity all the time). I need to show status bar with proper orientation. I do this by setting status bar orientation property in UIApplication and changing frame of opengl view so the view won't go under status bar. When I change from landscape to portrait (landscape is the initial state) view's frame is set to (0, 20, 320, 460) and stays like this. However view appears to be translated by (-10, -10). It seems that I did change the size of view but couldn't move it. Weird things are: initialy view is full screen, I change it to (0, 0, 300, 480) (landscape with status bar) and it works then, it doesn't work when I try to chenge it for the second time (portrait with status bar) frame property of the view shows that view is placed correctly Any thoughts on what can by the problem?

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• Entity Framework use of indexes and foreign keys

  - by David

  I want to be able to search a table quite quickly using the Entity Framework, say if I have a Contacts table, a JobsToDo table and a matrix table linking the two tables e.g Contacts_JobsToDo_Mtx and I specify two foreign keys in the Contacts_JobsToDo_Mtx table, if I wanted to search this Mtx table, do I need to specify an index on the two foreign keys? Or by the fact that they are two foreign keys are they considered indexed on them anyway? Will the Entity Framework be able to search through the Mtx table quickly without having to specfiy an index on both keys? Thanks!

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• How to optimize MATLAB loops?

  - by striglia

  I have been working lately on a number of iterative algorithms in MATLAB, and been getting hit hard by MATLAB's performance (or lack thereof) when it comes to loops. I'm aware of the benefit of vectorizing code when possible, but are there any tools for optimization when you need the loop for your algorithm? I am aware of the MEX-file option to write small subroutines in C/C++, although given my algorithms, this can be a very painful option given the data structures required. I mainly use MATLAB for the simplicity and speed of prototyping, so a syntactically complex, statically typed language is not ideal for my situation. Are there any other suggestions? Even other languages (python?) which have relatively painless matrix tools are an option.

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• vectorization of a text file

  - by Fox

  I am trying to implement vectorization of a text file...I have created a dictionary (Unique words in all the documents) ... Which is the best way to implement this in java? For example - My dictionary has the following words - {w1, w2, w3, w4} And I have 2 documents each having subset of the words in the vocabulary. I need to write to a text file the matrix in the form -- 1,3,4,0 0,0,2,1 Here each row represents a document and the values represent the occurrence of each word in the document. Can you suggest me the most efficient way to implement this in Java?

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• Changing text size on a ggplot bump plot

  - by Tom Liptrot

  Hi, I'm fairly new to ggplot. I have made a bumpplot using code posted below. I got the code from someones blog - i've lost the link.... I want to be able to increase the size of the lables (here letters which care very small on the left and right of the plot) without affecting the width of the lines (this will only really make sense after you have run the code) I have tried changing the size paramater but that always alter the line width as well. Any suggestion appreciated. Tom require(ggplot2) df<-matrix(rnorm(520), 5, 10) #makes a random example colnames(df) <- letters[1:10] Price.Rank<-t(apply(df, 1, rank)) dfm<-melt(Price.Rank) names(dfm)<-c( "Date","Brand", "value") p <- ggplot(dfm, aes(factor(Date), value, group = Brand, colour = Brand, label = Brand)) p1 <- p + geom_line(aes(size=2.2, alpha=0.7)) + geom_text(data = subset(dfm, Date == 1), aes(x = Date , size =2.2, hjust = 1, vjust=0)) + geom_text(data = subset(dfm, Date == 5), aes(x = Date , size =2.2, hjust = 0, vjust=0))+ theme_bw() + opts(legend.position = "none", panel.border = theme_blank()) p1 + theme_bw() + opts(legend.position = "none", panel.border = theme_blank())

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• NSString stringWithFormat: with C array?

  - by Chris Long

  Hi, I'm writing a program that calculates the Jacobi algorithm. It's written in Objective-C since it runs on a Mac, but the majority is written in standard C. I'm using a two-dimensional C array and an NSArray containing 5 NSTextField labels. The following code yields an EXC_BAD_ACCESS error: for ( int i = 0; i < 5; i++ ) { NSString *resultString = [NSString stringWithFormat:@"%g", matrix[i][i] ]; [[resultLabels objectAtIndex:i] setStringValue:resultString]; // error line } Any help?

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• Comparing images using SIFT

  - by Luís Fernando

  I'm trying to compare 2 images that are taken from a digital camera. Since there may be movement on the camera, I want to first make the pictures "match" and then compare (using some distant function). To match them, I'm thinking about cropping the second picture and using SIFT to find it inside the first picture... it will probably have a small difference on scale/translation/rotation so then I'd need to find the transformation matrix that converts image 1 to image 2 (based on points found by SIFT) any ideas on how to do that (or I guess that's a common problem that may have some opensource implementation?)? thanks

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• count of distinct acyclic paths from A[a,b] to A[c,d]?

  - by Sorush Rabiee

  I'm writing a sokoban solver for fun and practice, it uses a simple algorithm (something like BFS with a bit of difference). now i want to estimate its running time ( O and omega). but need to know how to calculate count of acyclic paths from a vertex to another in a network. actually I want an expression that calculates count of valid paths, between two vertices of a m*n matrix of vertices. a valid path: visits each vertex 0 or one times. have no circuits for example this is a valid path: but this is not: What is needed is a method to find count of all acyclic paths between the two vertices a and b. comments on solving methods and tricks are welcomed.

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• Matlab: Adding symbols to figure

  - by niko

  Hi, Below is the user interface I have created to simulate LDPC coding and decoding The code sequence is decoded iteratively by passing values between the left and right nodes through the connections. The first thing it would be good to add in order to improve visualization is to add arrows to the connections in the direction of passing values. The alternative is to draw a bigger arrow at the top of the connection showing the direction. Another thing I would like to do is displaying the current mathematical operation below the connection (in this example c * H'). What I don't know how to do is displaying special characters and mathematical symbols and other kinds of text such as subscript and superscript in the figure (for example sum sign and subscript "T" instead of sign ="'" to indicate transposed matrix). I would be very thankful if anyone could point to any useful resources for the questions above or show the solution. Thank you.

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• How to allow multiple inputs from user using R?

  - by Juan

  For example, if I need that the user specifies the number of rows and columns of a matrix: PROMPT: Number of rows?: USER INPUT: [a number] I need that R 'waits' for the input. Then save [a number] into a variable v1. Next, PROMPT: Number of columns?: USER INPUT: [another number] Also save [another number] into a variable v2. At the end, I will have two variables (v1, v2) that will be used in the rest of the code. "readline" only works for one input at a time. I can't run the two lines together v1 <- readline("Number of rows?: ") v2 <- readline("Number of columns?: ") Any ideas or suggestions? Thank you in advance

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• Maths: Determining angle in 3D space

  - by 742

  I hope this is the proper location to ask this question which is the same as this one, but expressed as pure math instead of graphically (at least I hope I translated the problem to math correctly). Considering: two vectors that are orthogonal: Up (ux, uy, uz) and Look (lx, ly, lz) a plane P which is perpendicular to Look (hence including Up) Y1 which is the projection of Y (vertical axis) along Look onto P Question: what is the value of the angle between Y1 and Up? As mathematicians will agree, this is a very basic question, but I've been scratching my head on walls now for at least two weeks without being able to visualize the solution... maybe now too old for finding solutions to school exercises. I'm looking for the scalar trigonometric solution, not a solution using a matrix. Thanks.

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• cmake: Target-specific preprocessor definitions for CUDA targets seems not to work

  - by Nils

  I'm using cmake 2.8.1 on Mac OSX 10.6 with CUDA 3.0. So I added a CUDA target which needs BLOCK_SIZE set to some number in order to compile. cuda_add_executable(SimpleTestsCUDA SimpleTests.cu BlockMatrix.cpp Matrix.cpp ) set_target_properties(SimpleTestsCUDA PROPERTIES COMPILE_FLAGS -DBLOCK_SIZE=3) When running make VERBOSE=1 I noticed that nvcc is invoked w/o -DBLOCK_SIZE=3, which results in an error, because BLOCK_SIZE is used in the code, but defined nowhere. Now I used the same definition for a CPU target (using add_executable(...)) and there it worked. So now the questions: How do I figure out what cmake does with the set_target_properties line if it points to a CUDA target? Googling around didn't help so far and a workaround would be cool..

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• MATLAB Heart Curve

  - by Arkapravo

  I am trying to get this in MATLAB, however I am not successful ! Any MATLAB gurus out there ? I guess simple commands should work, a program may not be needed. The error, I am getting is; >> t = -pi:0.1:pi; >> r = ((sin(t)*sqrt(cos(t)))*(sin(t) + (7/5))^(-1)) - 2*sin(t) + 2 ; ??? Error using ==> mtimes Inner matrix dimensions must agree.

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• Math/numerical formula every computer programmer should know

  - by aaa

  This is a follow-up question to What should every programmer know and Is mathematics necessary. So the question is, as a computer programmer, what is the most important/useful mathematical or numerical formula that you use? By Formula I mean anything that involves less obvious manipulations, whenever binomial coefficients or bit hacks. I work with multidimensional arrays and various matrix representations. So for me most commonly used formulas are: A(i,j,k,..) = a[i + j*Dim0 + k*Dim0*Dim1 + ... to map indexes to one dimension ( which is basic address calculation which many people do not seem to know). And triangular number T(i) = (i*i + i)/2 which is related to binomial coefficients, used to calculate address in triangular matrixes and many other things. What is your workhorse formula that you think programmer should know?

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• Code coordinates to match compass bearings

  - by pinnacler

  Right now in Matlab (0,0) is the origin, 0 degrees / 2pi would be to the right of the cartesian plane and angles are measured counter clockwise with 90 degrees being at the top. I'm trying to write a simulator where the coordinates would match a compass bearing. 0/360 degrees or 2pi would be at the top and 90 degrees would be on the right. Any idea how to code in Matlab or c++? I'd imaging it'd be a matrix flipped about the x axis and rotated 90 degrees but I'm at a total loss. Phil

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• How to compare a memory bits in C++?

  - by Trunet

  Hi, I need help with a memory bit comparison function. I bought a LED Matrix here with 4 x HT1632C chips and I'm using it on my arduino mega2560. There're no code available for this chipset(it's not the same as HT1632) and I'm writing on my own. I have a plot function that get x,y coordinates and a color and that pixel turn on. Only this is working perfectly. But I need more performance on my display so I tried to make a shadowRam variable that is a "copy" of my device memory. Before I plot anything on display it checks on shadowRam to see if it's really necessary to change that pixel. When I enabled this(getShadowRam) on plot function my display has some, just SOME(like 3 or 4 on entire display) ghost pixels(pixels that is not supposed to be turned on). If I just comment the prev_color if's on my plot function it works perfectly. Also, I'm cleaning my shadowRam array setting all matrix to zero. variables: #define BLACK 0 #define GREEN 1 #define RED 2 #define ORANGE 3 #define CHIP_MAX 8 byte shadowRam[63][CHIP_MAX-1] = {0}; getShadowRam function: byte HT1632C::getShadowRam(byte x, byte y) { byte addr, bitval, nChip; if (x>=32) { nChip = 3 + x/16 + (y>7?2:0); } else { nChip = 1 + x/16 + (y>7?2:0); } bitval = 8>>(y&3); x = x % 16; y = y % 8; addr = (x<<1) + (y>>2); if ((shadowRam[addr][nChip-1] & bitval) && (shadowRam[addr+32][nChip-1] & bitval)) { return ORANGE; } else if (shadowRam[addr][nChip-1] & bitval) { return GREEN; } else if (shadowRam[addr+32][nChip-1] & bitval) { return RED; } else { return BLACK; } } plot function: void HT1632C::plot (int x, int y, int color) { if (x<0 || x>X_MAX || y<0 || y>Y_MAX) return; if (color != BLACK && color != GREEN && color != RED && color != ORANGE) return; char addr, bitval; byte nChip; byte prev_color = HT1632C::getShadowRam(x,y); bitval = 8>>(y&3); if (x>=32) { nChip = 3 + x/16 + (y>7?2:0); } else { nChip = 1 + x/16 + (y>7?2:0); } x = x % 16; y = y % 8; addr = (x<<1) + (y>>2); switch(color) { case BLACK: if (prev_color != BLACK) { // compare with memory to only set if pixel is other color // clear the bit in both planes; shadowRam[addr][nChip-1] &= ~bitval; HT1632C::sendData(nChip, addr, shadowRam[addr][nChip-1]); shadowRam[addr+32][nChip-1] &= ~bitval; HT1632C::sendData(nChip, addr+32, shadowRam[addr+32][nChip-1]); } break; case GREEN: if (prev_color != GREEN) { // compare with memory to only set if pixel is other color // set the bit in the green plane and clear the bit in the red plane; shadowRam[addr][nChip-1] |= bitval; HT1632C::sendData(nChip, addr, shadowRam[addr][nChip-1]); shadowRam[addr+32][nChip-1] &= ~bitval; HT1632C::sendData(nChip, addr+32, shadowRam[addr+32][nChip-1]); } break; case RED: if (prev_color != RED) { // compare with memory to only set if pixel is other color // clear the bit in green plane and set the bit in the red plane; shadowRam[addr][nChip-1] &= ~bitval; HT1632C::sendData(nChip, addr, shadowRam[addr][nChip-1]); shadowRam[addr+32][nChip-1] |= bitval; HT1632C::sendData(nChip, addr+32, shadowRam[addr+32][nChip-1]); } break; case ORANGE: if (prev_color != ORANGE) { // compare with memory to only set if pixel is other color // set the bit in both the green and red planes; shadowRam[addr][nChip-1] |= bitval; HT1632C::sendData(nChip, addr, shadowRam[addr][nChip-1]); shadowRam[addr+32][nChip-1] |= bitval; HT1632C::sendData(nChip, addr+32, shadowRam[addr+32][nChip-1]); } break; } } If helps: The datasheet of board I'm using. On page 7 has the memory mapping I'm using. Also, I have a video of display working.

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• Resizing page format on iReport

  - by pringlesinn

  I've been trying to print a pdf made from iReport in less than a page A4. it's like half A4 page height. I'm using a Line Matrix printer, doesn't matter which one. So, when I try to print 2 files at same file, it should print everything on the right place, but just first file is printed correctly. The second one is based on a A4 page format, and just starts printing after A4 page height is over, skipping a big blank. Where can I set the size of page in iReport? The only thing I could do was setting size of what is shown on screen while I edit the file. I tried my best to explain the situation, any doubts, ask me and I'll try even harder.

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• What is the best Java numerical method package?

  - by Bob Cross

  I am looking for a Java-based numerical method package that provides functionality including: Solving systems of equations using different numerical analysis algorithms. Matrix methods (e.g., inversion). Spline approximations. Probability distributions and statistical methods. In this case, "best" is defined as a package with a mature and usable API, solid performance and numerical accuracy. Edit: derick van brought up a good point in that cost is a factor. I am heavily biased in favor of free packages but others may have a different emphasis.

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• 3D Math: Calculate Bank (Roll) angle from Look and Up orthogonal vectors

  - by 742

  I hope this is the proper location to ask this question which is the same as this one, but expressed as pure math instead of graphically (at least I hope I translated the problem to math correctly). Considering: two vectors that are orthogonal: Up (ux, uy, uz) and Look (lx, ly, lz) a plane P which is perpendicular to Look (hence including Up) Y1 which is the projection of Y (vertical axis) along Look onto P Question: what is the value of the angle between Y1 and Up? As mathematicians will agree, this is a very basic question, but I've been scratching my head for at least two weeks without being able to visualize how to project Y onto P... maybe now too old for finding solutions to school exercises. I'm looking for the trigonometric solution, not a solution using a matrix. Thanks.

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• min max coordinate of cells , given cell length in c#

  - by Raj

  Please see attached picture to better understand my question i have a matrix of cells of [JXI] , cell is square in shape with length "a" my question is .. is there a way to use FOR loop to assign MIN,MAX coordinate to each cell taking origin (0,0) at one corner Thanks "freeimagehosting.net/uploads/3b09575180.jpg" i was trying following code but no success int a ; a = 1; for (int J=1; J<=5; J++) { for (int I = 1; I <= 5; I++) { double Xmin = ((I - 1)*a ); double Ymin = ((J - 1) * a); double Xmax = (I * a ); double Ymax = (J * a); } }

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• Jasper Reports Crosstab Query

  - by Sean McDaid

  I'm using Jasper Reports/iReports crosstabs to create a matrix of student and results. So for example Jim is doing subjects A, B, C and Sally is doing A, C What I want is something like: Subj-A Subj-B Subj-C Jim P M D Sally D D But as my SQL orders by name then subject I get: Subj-A Subj-B Subj-C Subj-A Subj-C Jim P M D Sally D D As you can see in the above the results are correct but the formatting is woeful. Is there anyway I can generate the reports to use names and subject only once and filling in the values from here? This probably isn't clear.

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• Implement a Cellular Automaton ? "Rule 110"

  - by ZaZu

  I was wondering how to use the Rule 110, with 55 lines and 14 cells. I have to then display that in an LED matrix display. Anyway my question is, how can I implement such automaton ?? I dont really know where to start, can someone please shed some light on how can I approach this problem ? Is there a specific METHOD I must follow ? Thanks --PROGRAM USED IS - C EDIT char array[54][14]; for(v=0;v<55;v++){ for(b=0;b<15;b++){ if(org[v][b-1]==0 && org[v][b]==0 && org[v][b+1] == 0) { array[v][b]=0; } array[v][b]=org[v][b]; } } Does that make sense ?? org stands for original

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• plot 3D and combine in matlab

  - by George

  Hello ,i have this matrix "experiment=2*rand(npoints,3)-1". I want to plot in in 3D,so i use "mesh(experiment)". How can i take red points in my plot? Also,i want to implement in the above plot , a sphere with radius 1 at 0,0,0. I did : mesh(experiment) hold on [x,y,z]=sphere; r=1; mesh(r*x,r*y,r*z) hold off but 1) i am not taking radius 1 2) the figures just showing in the same graph but don't combine Thanks

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