How to get different colours in a matrix with imagesc?

Question

Dave 2018-11-10

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/429121-how-to-get-different-colours-in-a-matrix-with-imagesc

回答： Dave 2018-11-11

采纳的回答： jonas

在 MATLAB Online 中打开

Hello,

i created a matrix and within the matrix there is a circle of red dots.

i need all the dots to have different colours (red, blue, green) on a random basis, but i dont know how to do it.

here is my code:

m1 = zeros(400,400,3); 
center = round(size(m1)/2); 
ecc = (rand(1,1000).^0.5).*100;  
pol = rand(1,1000).*360;
x = round(cosd(pol) .* ecc); y = round(sind(pol) .* ecc);
m1(sub2ind(size(m1),center(1)-y, center(2)+x)) = 3;
figure; imagesc(m1)

i want to do it with a "for" loop like this

for i = 1:3
ecc = (rand(1,1000).^0.5).*100, i;  
pol = rand(1,1000).*360, i;
end

or something like this:

for i = 1:3
ecc = (rand(1,1000, i).^0.5).*100;  
pol = rand(1,1000, i).*360;
end

i am very new to matlab and i even fail to figure out where in this code the colour can be placed.

i just know that colour for a very simple matrix works like this:

mat(3,4,1) = 1;     %red
mat(5,6,2) = 1;     %green
mat(1,2,3) = 1;     %blue

thanks for help :)

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Answer 1

jonas 2018-11-10

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/429121-how-to-get-different-colours-in-a-matrix-with-imagesc#answer_346241

编辑：jonas 2018-11-10

在 MATLAB Online 中打开

I made an attempt at fixing your code. What you describe with colors is for RGB images, to display with imshow not imagesc. For imagesc you can simply work with 2D matrices and a suitable colormap.

m1 = zeros(400,400,1); 
center = round(size(m1)/2); 
ecc = (rand(1,1000).^0.5).*100;  
pol = rand(1,1000).*360;
x = round(cosd(pol) .* ecc); y = round(sind(pol) .* ecc);
m1(sub2ind(size(m1),center(1)-y, center(2)+x)) = randi([1 3],1,1000);
figure; 
colormap([0 0 0;1 0 0;0 1 0;0 0 1])
imagesc(m1)