# how to only plot a certain area of an existing plot

5 views (last 30 days)
rman on 30 Jun 2022
Commented: rman on 1 Jul 2022
Hi, so i have this figure which is produced from my code (attached). I would like to reproduce the plot but for it to be masked within a circle and for the data points to only be plotted within this circle. The circle is to have a radius of 0.045m and the centre is to be located at (0,0). I have also attached an image of what kind of thing I am after.
Thank you in advance! I have attached my code.
n = 250; % number of points on the voronoi diagram
L2x = zeros(1,n); % array to store the L2 x values
L2y = zeros(1,n); % array to store the L2 y values
for i=1:n
q = randi([-50 50],1,1); %Parameters for the random case
L2x(i) = q.*1e-3 ; %limit that L2 must be greater than 0.5mm is obeyed
w = randi([-50 50],1,1);
L2y(i) = w.*1e-3;
P = [L2x(:) L2y(:)]; %extracting the x and y values and placing it into one matrix
end
figure
voronoi(P(:,1),P(:,2)) % Plotting the voronoi diagram
[V,C] = voronoin(P); % storing the voroni vertexs' in V
V(isinf(V)) = 1; % replacing the inf values in the array to 1
for i=1:length(C) %finding the centroids for each cell
Cnew = V(C{i},:);
[xnew,ynew] = centroid(polyshape(Cnew(:,1),Cnew(:,2)));
% m = (x)
hold on
plot(xnew,ynew,'r+')
axis ([-0.050 0.050 -0.050 0.050])
hold off
end

Sam Chak on 30 Jun 2022
Generally, this imcrop() command is used to crop image, but it can only crop rectangular shape.
To crop a circular shape out of the image, you need some tricks.
Follow the procedure as detailed by out community's best @Image Analyst. (no pun intended).
rman on 1 Jul 2022
Im afraid this isnt exactly what im after. I am not after saving the image and cropping the image. Im trying to produce the first plot but write a script that only plots the points within the circle and then doesnt plot anything which is not inside it.

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