Generate a sector mask within a big matrix

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Ankit Labh
Ankit Labh 2019-12-11
评论： Ankit Labh 2019-12-11
A sector mask is defined by distance and angle. Please see the image for clarification on mask.
I want to generate a 100 by 100 matrix where all the matrix element inside the mask is 1 otherwise 0.
MASK.png
Thanks.
  2 个评论
Looky
Looky 2019-12-11
Do you already have the coordinates as show in the image? Then just convert to polar using cart2pol and afterwards use some simple logic to check for radius and the angle.

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Looky
Looky 2019-12-11
编辑：Looky 2019-12-11
Solution could look like this:
% Generate example coordinates
x=linspace(-1,1,100);
y=fliplr(linspace(-1,1,100));
[X,Y]=meshgrid(x,y);
% Parameters for sector
angle=10;
radiusIn=.8;
radiusOut=.2;
% Coordinates to polarcoordinates
[phi, rho]=cart2pol(X,Y);
phi=rad2deg(phi);
phi(phi<0)=-phi(phi<0);
% Generate mask
mask=rho>radiusOut & rho<radiusIn & phi>angle& phi<180-angle;
% Have a look at the mask
spy(mask);
For your problem you should exchange the first part of generating the X and Y values for your own coordinates. Otherwise the mask might not be centered the way your data is.
  1 个评论
Ankit Labh
Ankit Labh 2019-12-11
Dear Looky,
Many thanks for your answer. It worked. I got many new ideas for other questions.
best regards,
Ankit

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