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Find the indices of elements within a submatrix of a larger matrix

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Stephanie Diaz
Stephanie Diaz 2019-5-3
评论： Stephanie Diaz 2019-5-3
Say I have a matrix "B" of ones and zeros and I find a smaller submatrix (with a "range" or radius of 60 cells) within "B" using the following, where "xpos" and "ypos" are x and y coordinates within "B". As an example, if my "xpos" is 1000 and "ypos" is 1000, I form a 60 cell submatrix around this position and call it "B_sub"
subx = max(1,xpos-range):min(n1,xpos+range);
suby = max(1,ypos-range):min(n2,ypos+range);
B_sub = B(subx,suby); %This is the submatrix around matrix B
I would like to find all zeroes in the submatrix, and I do this by the following:
xidx=find(B(subx,suby)==0);
"xidx" gives me the linear indices of zeros within the submatrix "B_sub", but I want to know what the subscript indices of these elements are within the larger matrix "B". I have tried ismember and intersect, but do not get the output I need.
  2 个评论
Adam
Adam 2019-5-3
Can't you just add max(1,xpos-range) to x and max(1,ypos-range) to y if you use the two output variant of the find function?
Stephanie Diaz
Stephanie Diaz 2019-5-3
I believe the output variant returns only the linear indices of the zero elements. Do I add these indices to max(1,xpos- range) and max(ypos-range)?

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