MATLAB: Creating random points in a circle

circlegridtemperature

I am new to MatLab but I am trying to write code for a problem and a couple of things are sticking me up. I am trying to create X number of random points within a circle. The purpose being to model a camp fire and map temperature from the center of the circle at the hottest to the outside. And I am lost. And I can't find an example anywhere I might be able to pull apart and work with. And help would be very much appreciated.

Thanks!

Best Answer

Let the circle be of radius R and center at (x0,y0). Let n be the desired number of points within.

 t = 2*pi*rand(n,1);
 r = R*sqrt(rand(n,1));
 x = x0 + r.*cos(t);
 y = y0 + r.*sin(t);
 plot(x,y)

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Try this:

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close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
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format longg;
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%===============================================================================
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MATLAB: Plotting multiple gaussians on an image

image is the name of a built-in function. Don't use image as the name of your variable.

Don't use uint8 as your image's data class. Let your images be double. Then display with

imshow(yourImage, []);

Here's an old demo of mine that does it, for what it's worth....

% M-file to place multiple small circles of Gaussian profile
% inside a big circle. 
% Clean up 
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
imtool close all;  % Close all imtool figures.
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 14;
% Initialize some parameters. 
numberOfSmallCircles = 50; % Number of small circles 
smallCircleOutsideValue = 0.3; 
smallCircleInsideValue = 0.8; 
smallCircleRadius = 31;    % small circle radius 
bigImageWidth = 500; 
bigImageHeight =  500; % square area 0f 500*500 
bigCircleRadius = 250;    % big circle radius 
% Initialize an image to hold one single big circle. 
bigCircleImage = zeros(bigImageHeight, bigImageWidth); 
[x, y] = meshgrid(1:bigImageWidth, 1:bigImageHeight); 
bigCircleImage((x - bigImageWidth/2).^2 + (y - bigImageHeight/2).^2 <= bigCircleRadius.^2) = 1; 
% Display it in the upper left plot. 
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imshow(bigCircleImage, []); 
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sigma = smallCircleRadius * .4;
singleCircleImage = fspecial('gaussian', 2*smallCircleRadius, sigma); 
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subplot(3,2,2); 
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axis on;
singleWidth = size(singleCircleImage, 2); 
singleHeight = size(singleCircleImage, 1); 
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heightThatWillFit = bigImageHeight - 2 * smallCircleRadius; 
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smallUpperLeftY = heightThatWillFit * rand(numberOfSmallCircles, 1); 
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for k = 1 : numberOfSmallCircles 
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        end
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subplot(3,2,4); 
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axis on;
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subplot(3,2,5:6);
numberOfBins = 128;
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bar(pixelCounts);
xlim([1 numberOfBins]);
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Best Answer

Related Solutions

MATLAB: Adding Noise to the Image

MATLAB: Plotting multiple gaussians on an image

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