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Central part of a matrix

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Auryn_
Auryn_ 2015-2-24
评论： Sean de Wolski 2015-2-25
Hello,
If a have a Matrix M and I want to create a new one, call it Central_M, which should be the central part of M and of a defined size s, how can I do it?
M_central = ?
Thanks in advance for your reply.
  2 个评论
Chris McComb
Chris McComb 2015-2-24
What exactly do you mean by 'central'? And can you define s?
Auryn_
Auryn_ 2015-2-25
Central means that I want to take only the central part of the matrix of a defined size s. s = imcrop(I,[max(1,i-10) max(1,j-10) 23 23]);

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回答（2 个）

Jos (10584)
Jos (10584) 2015-2-25
Something like this?
M = spiral(10) % test matrix
S = 2 % s elements around the central position
% the resulting matrix will be 2*S+1 squared in size
dx = -S:S ;
RC0 = ceil(size(M)/2) % central position
OUT = M(RC0(1)+dx, RC0(2)+dx)
RAGHAVENDRA
RAGHAVENDRA 2015-2-25
编辑：Guillaume 2015-2-25
M_central=M(floor(size(M,1)/2)-floor(s/2):floor(size(M,1)/2)+floor(s/2),floor(size(M,2)/2)-floor(s/2):floor(size(M,2)/2)+floor(s/2));
The above instruction will work, you can use 'round' instead of 'floor' to change the matrix indices accordingly.
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Auryn_
Auryn_ 2015-2-25
I receive an error message :(
RAGHAVENDRA
RAGHAVENDRA 2015-2-25
编辑：RAGHAVENDRA 2015-2-25
It is working perfectly for me, this is the example that i have tried
M=randi(5,[10 10]);
s=2;
M_central=M(floor(size(M,1)/2)-floor(s/2):floor(size(M,1)/2)+floor(s/2),floor(size(M,2)/2)-floor(s/2):floor(size(M,2)/2)+floor(s/2))
What is the error message?

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