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  • Graphing special functions in Matlab (2D Bessel)

    - by favala
    I'm trying to essentially get something like this where I can see clear ripples at the base but otherwise it's like a Gaussian: This is kind of unsatisfactory because the ripples aren't very noticeable, it has a very gritty quality that obscures the image a bit, and if you move the graph so that it's just in 2D (so it looks like a circle) I'm not even sure if it's quite like how it should be (the concentric circles seem to be more evenly spaced in the real thing). So, is there a better way to do this? a = 2*pi; [X Y] = meshgrid(-1:0.01:1,-1:0.01:1); R = sqrt(X.^2+Y.^2); f = (2*besselj(1,a*R(:))./R(:)).^2; mesh(X,Y,reshape(f,size(X))); axis vis3d;

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  • MATLAB pdist function

    - by James
    Hi, I am using the pdist command to find the distance between x and y coordinates stored in a matrix. X = [100 100; 0 100; 100 0; 500 400; 300 600;]; D = pdist(X,'euclidean') Which returns a 15 element vector. : [0.734979755525412 3.40039811339820 2.93175207511321 1.83879677592575 2.40127440268306 2.75251513299386 2.21488402640753 1.10610649500317 1.81674017301699 0.903207751535635 1.99116952754924 1.05069952386082 1.24122819418333 1.08583377275532 1.38729428638035] Is there a way to associate these distances with the coordinates they were derived from, i.e. store them in a matrix with the general row form: [Length xcoordinate1 ycoordinate1 xcoordinate2 ycoordinate2] Where there is a row for each length found? Thanks in advance

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  • matlab: simple matrix filtering - group size

    - by Art
    I have a huuuge matrix storing information about X and Y coordinates of multiple particle trajectories , which in simplified version looks like that: col 1- track number; col 2- frame number; col 2- coordinate X; col 3- coordinate Y for example: A = 1 1 5.14832 3.36128 1 2 5.02768 3.60944 1 3 4.85856 3.81616 1 4 5.17424 4.08384 2 1 2.02928 18.47536 2 2 2.064 18.5464 3 1 8.19648 5.31056 3 2 8.04848 5.33568 3 3 7.82016 5.29088 3 4 7.80464 5.31632 3 5 7.68256 5.4624 3 6 7.62592 5.572 Now I want to filter out trajectories shorter than lets say 2 and keep remaining stuff like (note renumbering of trajectories): B = 1 1 5.14832 3.36128 1 2 5.02768 3.60944 1 3 4.85856 3.81616 1 4 5.17424 4.08384 2 1 8.19648 5.31056 2 2 8.04848 5.33568 2 3 7.82016 5.29088 2 4 7.80464 5.31632 2 5 7.68256 5.4624 2 6 7.62592 5.572 How to do it efficiently? I can think about some ideas using for loop and vertcat, but its the slowest solution ever :/ Thanks!

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  • matlab: putting a circled number onto a graph

    - by Jason S
    I want to put a circled number on a graph as a marker near (but not on) a point. Sounds easy, but I also want to be invariant of zoom/aspect ratio changes. Because of this invariant, I can't draw a circle as a line object (without redrawing it upon rescale); if I use a circle marker, I'd have to adjust its offset upon rescale. The simplest approach I can think of is to use the Unicode or Wingdings characters ① ② ③ etc. in a string for the text() function. But unicode doesn't seem to work right, and the following sample only works with ① and not for the other numbers (which yield rectangle boxes): works: clf; text(0.5,0.5,char(129),'FontName','WingDings') doesn't work (should be a circled 2): clf; text(0.5,0.5,char(130),'FontName','WingDings') What gives, and can anyone suggest a workaround?

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  • MATLAB syntax of (:)

    - by user198729
    >> I=[2 1 3;3 2 4] I = 2 1 3 3 2 4 >> I(:) ans = 2 3 1 2 3 4 >> I(1:2) ans = 2 3 >> Why the first call I(:) returns a vector while the second I(1:2) doesn't which is essentially the same as I(:)?

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  • 3x3 Average filter in matlab

    - by turingcomplete
    I've written code to smooth an image using a 3x3 averaging filter, however the output is strange, it is almost all black. Here's my code. function [filtered_img] = average_filter(noisy_img) [m,n] = size(noisy_img); filtered_img = zeros(m,n); for i = 1:m-2 for j = 1:n-2 sum = 0; for k = i:i+2 for l = j:j+2 sum = sum+noisy_img(k,l); end end filtered_img(i+1,j+1) = sum/9.0; end end end I call the function as follows: img=imread('img.bmp'); filtered = average_filter(img); imshow(uint8(filtered)); I can't see anything wrong in the code logic so far, I'd appreciate it if someone can spot the problem.

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  • MATLAB help required function root

    - by programmeur
    Dear All, I have made an program, function bisection; x1=input('enter the first value=') x2=input('enter the second value=') %f3=[]; for x=1:20 %x=1; x3=(x1+x2)/2; while x3-x1 >= 0.001 f3(x)=x3^3 + x3^2 - 3*x3 - 3; f1(x)=x1^3 + x1^2 - 3*x1 - 3; if ((f3(x)*f1(x)) < 0) x2=x3; else x1=x3; end break end format long f3' disp('The root is found to be ='); x3 end . . . . . program calculate function of interval (x1, x2) given by user, my program compile and execute but little stupid repetition until for loop complete, i want to stop further printing loop when desired value is achieved with while condition is used.

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  • Weighted random numbers in MATLAB

    - by yuk
    How to randomly pick up N numbers from a vector a with weight assigned to each number? Let's say: a = 1:3; % possible numbers weight = [0.3 0.1 0.2]; % corresponding weights In this case probability to pick up 1 should be 3 times higher than to pick up 2. Sum of all weights can be anything.

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  • radio button group matlab

    - by vijisai
    i have two set of button groups. first button groups has two radio buttons and second group has four radio buttons. if button 1 is selected in group1 and any one from the group 2. similarly for button2 in group 1 and any one from group2, respective function calls must be made on click of push button with these combinations. how to do it. there will be 8 separate function calls for their respective combinations. how to do the combination of button groups. switch case or if else statement did not work out?? kindly help.

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  • Help in optimizing a for loop in matlab

    - by HH
    I have a 1 by N double array consisting of 1 and 0. I would like to map all the 1 to symbol '-3' and '3' and all the 0 to symbol '-1' and '1' equally. Below is my code. As my array is approx 1 by 8 million, it is taking a very long time. How to speed things up? [row,ll] = size(Data); sym_zero = -1; sym_one = -3; for loop = 1 : row if Data(loop,1) == 0 Data2(loop,1) = sym_zero; if sym_zero == -1 sym_zero = 1; else sym_zero = -1; end else Data2(loop,1) = sym_one; if sym_one == -3 sym_zero = 3; else sym_zero = -3; end end end

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  • Add inputs to more than one row in a cell array in matlab

    - by ZaZu
    Hi there, I would like to know how can I get certain inputs and put them in more than one row in the cell array ... I basically want an array that updates one input per row in ever loop. The loop is looped 30 times, so I want to have 30 rows and 2 columns ( x and y columns) I have this code : For N=1:30 . . . Binary = bwlabel(blacknwhite); s = regionprops(Binary,'centroid'); centroids = cat(1, s.Centroid); hold(imgca,'on') plot(imgca,centroids(1,1), centroids(1,2),'r*') . . . end I dont think this does what I want ... only the first row is updated in my loop .. So how can I create this cell array ? If you want more info please tell me and I will update it right away. Thanks !

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  • Add inputs to more than one row in a structure array in matlab

    - by ZaZu
    Hi there, I would like to know how can I get certain inputs and put them in more than one row in the structure ... I basically want a structure that updates one input per row in ever loop. The loop is looped 30 times, so I want to have 30 rows and 2 columns ( x and y columns) I have this code : For N=1:30 . . . Binary = bwlabel(blacknwhite); s = regionprops(Binary,'centroid'); centroids = cat(1, s.Centroid); hold(imgca,'on') plot(imgca,centroids(1,1), centroids(1,2),'r*') . . . end I dont think this does what I want ... only the first row is updated in my loop .. So how can I create this structure ? If you want more info please tell me and I will update it right away. Thanks !

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  • convert string array to cell in MATLAB

    - by Maddy
    I need to output a cell to an excel file. Before this I need to convert a date column of integers to datestrings. I know how to do this, but I am not able to put this new string array back into the cell - mycell = { 'AIR' [780] [1] [734472] [0.01] ; ... 'ABC' [780] [1] [734472] [0.02]} I did this -- dates = datestr(cell2mat(mycell(:,4))) ; What I need as an answer is: {'AIR' [780] [1] '14-Dec-2010' [0.01] ; 'ABC' [780] [1] '23-Dec-2010' [0.03] ; } so that I can now send it to an excel file using xlswrite.m

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  • matlab noise cleaning

    - by gil
    how can i clean image from noise? i have a program that create images, and i have noises in the images, like a shadow of the object that in the image. how can i clean it? i tried to use a level, but i didn't work.

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  • For loops in Matlab

    - by seidel
    I run through a for loop, each time extracting certain elements of an array, say element1, element2, etc. How do I then pool all of the elements I've extracted together so that I have a list of them?

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  • What does L == 2 mean in MATLAB?

    - by Matlaber
    BW = logical([1 1 1 0 0 0 0 0 1 1 1 0 1 1 0 0 1 1 1 0 1 1 0 0 1 1 1 0 0 0 1 0 1 1 1 0 0 0 1 0 1 1 1 0 0 0 1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 0 0 0]); L = bwlabel(BW,4); [r,c] = find(L == 2); How can a matrix been compared with scalar?

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  • How can I find the value of a blury image Matlab question

    - by user332447
    Is there a method to detect the value of a image rgb that is blury? I simply want to store the blury value of my image in a variable called blury value? Is there a dedicated function? %image1 which is rgb is stored in variable img1 img1 = imread('102.jpg'); % conversion to grayscale stored in img1_grey variable img1_grey = rgb2gray(img1); blury_value = function_matlab(img1)

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  • Subplots of multidimensional arrays in Matlab

    - by altes4ia
    I have a 10x10x10 array, z. How do I plot everything in the SAME window so that I would have the 3 plots for z(:,:,1) and below it the three plots for z(:,:,2) etc ? This is what I have so far: for i = 1:10 z=z(:,:,i); figure(i) subplot(1,2,1) surf(z) %code, obtain new array called "new1"... subplot(1,2,2) surf(new1) %code, obtain new array called "new2"... subplot(1,3,3) surf(new2) end;

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  • Matlab: plotting frequency distribution with a curve

    - by Kaly
    I have to plot 10 frequency distributions on one graph. In order to keep things tidy, I would like to avoid making a histogram with bins and would prefer having lines that follow the contour of each histogram plot. I tried the following [counts, bins] = hist(data); plot(bins, counts) But this gives me a very inexact and jagged line. I read about ksdensity, which gives me a nice curve, but it changes the scaling of my y-axis and I need to be able to read the frequencies from the y-axis. Can you recommend anything else?

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