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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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• 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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• How to share a variable between two classes?

  - by Altefquatre

  How would you share the same object between two other objects? For instance, I'd like something in that flavor: class A { private string foo_; // It could be any other class/struct too (Vector3, Matrix...) public A (string shared) { this.foo_ = shared; } public void Bar() { this.foo_ = "changed"; } } ... // inside main string str = "test"; A a = new A(str); Console.WriteLine(str); // "test" a.Bar(); Console.WriteLine(str); // I get "test" instead of "changed"... :( I read there is some ref/out stuff, but I couldn't get what I'm asking here. I could only apply some changes in the methods scope where I was using ref/out arguments... I also read we could use pointers, but is there no other way to do it?

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• MATLAB submatrix over variable dimensions

  - by rlbond

  I have a variable dimension matrix, X. I want a function that will get the first half of X in one dimension. I.E., I want something like this: function x = variableSubmatrix(x, d) if d == 1 switch ndims(x) case 1 x = x(1:end/2); case 2 x = x(1:end/2, :); case 3 x = x(1:end/2, :, :); (...) end elseif d == 2 switch ndims(x) case 2 x = x(:, 1:end/2); case 3 x = x(:, 1:end/2, :); (...) end elseif (...) end end I'm not quite sure how to do this. I need it to be fast, as this will be used many times in computation.

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• Which machine learning library to use

  - by Space_C0wb0y

  I am looking for a library that, ideally, has the following features: implements hierarchical clustering of multidimensional data (ideally on similiarity or distance matrix) implements support vector machines is in C++ is somewhat documented (this one seems to be hardest) I would like this to be in C++, as I am most comfortable with that language, but I will also use any other language if the library is worth it. I have googled and found some, but I do not really have the time to try them all out, so I want hear what other people had for experiences. Please only answer if you have some experience with the library you recommend. P.S.: I could also use different libraries for the clustering and the SVM.

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• Why wouldn't `new int[x]{}` be valid???

  - by dboarman-FissureStudios

  In MonoDevelop I have the following code which compiles: int[] row = new int[indices.Count]{}; However, at run-time, I get: Matrix.cs(53,53): Error CS0150: A constant value is expected (CS0150) (testMatrix) I know what this error means and forces me to then resize the array: int[] row = new int[indices.Count]{}; Array.Resize(ref row, rowWidth); Is this something I just have to deal with because I am using MonoDevelop on Linux? I was certain that under .Net 3.5 I was able to initialize an array with a variable containing the width of the array. Can anyone confirm that this is isolated? If so, I can report the bug to bugzilla.

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• Is it safe to use the same parameters for input and output in D3DX functions?

  - by JB

  Using the D3DX library that is a part of directX, specifically directx9 in this case, I'm wondering if it's safe to use the same matrix (or vector etc) for input and ouput D3DXMATRIX mat; D3DXMatrixInverse(&mat, NULL, &mat); I've been avoiding doing so, assuming that it would result in bad things happening when parts of the array got partly overwritten as results are calculated but I see an awful lot of code around that does exactly this. A brief test indicates that it seems to work ok, so I'm assuming that the D3DX functions take a copy where necessary of the input data, or some other method to ensure that this works ok, but I can't find it documented anywhere so I'm reluctant to rely on it working. Is there any official statement on using the functions like this?

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• Why might different computers calculate different arithmetic results in VB.NET?

  - by Eyal

  I have some software written in VB.NET that performs a lot of calculations, mostly extracting jpegs to bitmaps and computing calculations on the pixels like convolutions and matrix multiplication. Different computers are giving me different results despite having identical inputs. What might be the reason? Edit: I can't provide the algorithm because it's proprietary but I can provide all the relevant operations: ULong \ ULong (Turuncating division) Bitmap.Load("filename.bmp') (Load a bitmap into memory) Bitmap.GetPixel(Integer, Integer) (Get a pixel's brightness) Double + Double Double * Double Math.Sqrt(Double) Math.PI Math.Cos(Double) ULong - ULong ULong * ULong ULong << ULong List.OrderBy(Of Double)(Func) Hmm... Is it possible that OrderBy is using a non-stable QuickSort and that QuickSort is using a random pivot? Edit: Just tested, nope. The sort is stable.

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• How do I draw an ellipse with arbitrary orientation pixel by pixel?

  - by amc

  Hi, I have to draw an ellipse of arbitrary size and orientation pixel by pixel. It seems pretty easy to draw an ellipse whose major and minor axes align with the x and y axes, but rotating the ellipse by an arbitrary angle seems trickier. Initially I though it might work to draw the unrotated ellipse and apply a rotation matrix to each point, but it seems as though that could cause errors do to rounding, and I need rather high precision. Is my suspicion about this method correct? How could I accomplish this task more precisely? I'm programming in C++ (although that shouldn't really matter since this is a more algorithm-oriented question).

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• best method of turning millions of x,y,z positions of particles into visualisation

  - by Griff

  I'm interested in different algorithms people use to visualise millions of particles in a box. I know you can use Cloud-In-Cell, adaptive mesh, Kernel smoothing, nearest grid point methods etc to reduce the load in memory but there is very little documentation on how to do these things online. i.e. I have array with: x,y,z 1,2,3 4,5,6 6,7,8 xi,yi,zi for i = 100 million for example. I don't want a package like Mayavi/Paraview to do it, I want to code this myself then load the decomposed matrix into Mayavi (rather than on-the-fly rendering) My poor 8Gb Macbook explodes if I try and use the particle positions. Any tutorials would be appreciated.

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• Crystal Report with mutliple row columns.

  - by Jack

  I'm not sure if the title properly explains what I'm trying to do. I'm trying to move from using SQL Reporting Services to a Crystal Reports Web App. I've gotten some reports to design properly because they are simple cross-tab reports that require nothing special. I'm running into a little problem of a user matrix report. Here's how the report looks on SQL Reporting Services: group1 group2 group3 username1 first1 last1 title1 X X username2 first2 last2 title2 X X 2 1 1 Normally in VS2008 with a SQL rdl, I would right click on the row and Insert Column. However, i don't see a way to do this in Crystal Reports. I've tried setting up multiple row groups, but that adds mutliple groupings like: group1 Total ... Username Total ... first Total ... last ...

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• Python - Using "Google AJAX Search" API's Local Search Objects

  - by user330739

  Hi! I've just started using Google's search API to find addresses and the distances between those addresses. I used geopy for this, but, I often had the problem of not getting the correct addresses for my queries. I decided to experiment, therefore, with Google's "Local Search" (http://code.google.com/apis/ajaxsearch/local.html). Anyway, I wanted to ask if I could use the "Local Search" objects provided by the API within python. Something tells me that I can't and that I have to use json. Does anyone know if there is a work around? PS: Im trying to make something like this: http://www.google.com/uds/samples/random/lead.html ... except a matrix type deal where the insides will be filled with distances between the addresses. Thanks for reading!

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• Scale GraphicsPaths

  - by serhio

  In a form I draw a graph. This graph has some distinct paths that should have differently drawn. Say AxesPath, SalesPath, CostsPath etc... When I resize the form need I to scale every of components Paths? Take an example: Imports System.Drawing.Drawing2D Public Class Form1 Dim lineOne As GraphicsPath Dim lineTwo As GraphicsPath Dim allPaths As GraphicsPath Dim initSize As Size Public Sub New() ' This call is required by the designer. ' InitializeComponent() initSize = Me.Size lineOne = New GraphicsPath() lineTwo = New GraphicsPath() lineOne.AddLine(20.0F, 20.0F, Me.initSize.Width - 20.0F, 20.0F) lineTwo.AddLine(0.1F, 10.0F, Me.initSize.Width - 20.0F, _ Me.initSize.Height - 0.5F) allPaths = New GraphicsPath() allPaths.AddPath(lineOne, False) allPaths.AddPath(lineTwo, False) Me.ResizeRedraw = True End Sub Protected Overrides Sub OnResize(ByVal e As System.EventArgs) MyBase.OnResize(e) Dim m As New Matrix m.Scale(Me.Width / initSize.Width, Me.Height / initSize.Height) allPaths.Transform(m) initSize = Me.Size End Sub Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs) MyBase.OnPaint(e) ' WORKS ' ' e.Graphics.DrawPath(Pens.GreenYellow, allPaths) ' ' DOES NOT WORK! ' e.Graphics.DrawPath(Pens.DarkGoldenrod, lineOne) e.Graphics.DrawPath(Pens.DarkMagenta, lineTwo) End Sub End Class

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• invalid conversion from 'char' to 'int* in C

  - by majdal

  Hi, I have the following arrays: int A[] = {0,1,1,1,1, 1,0,1,0,0, 0,1,1,1,1}; int B[] = {1,1,1,1,1, 1,0,1,0,1, 0,1,0,1,0}; int C[] = {0,1,1,1,0, 1,0,0,0,1, 1,0,0,0,1}; //etc... for all letters of the alphabet And a function that prints the letters on a 5x3 LED matrix: void printLetter(int letter[]) I have a string of letters: char word[] = "STACKOVERFLOW"; and I want to pass each character of the string to the printLetter function. I tried: int n = sizeof(word); for (int i = 0; i < n-1; i++) { printLetter(word[i]); } But I get the following error: invalid conversion from 'char' to 'int*' What should i be doing? Thanks!!

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