Array Correlation - compute array difference with its neighbor elements

조회 수: 1 (최근 30일)
ichi
ichi 2017년 10월 29일
댓글: Walter Roberson 2017년 10월 30일
Hi,
Do you know the fastest way to compute array mean difference with its neighbor elements in a N x N matrix? and is there a possibility to perform for second neighbors, third and so on.
Suppose you have
a=[1 4 5 3 6 ; 8 10 0 9 11 ; 2 5 20 15 9 ; 8 12 4 6 0 ; 7 9 18 2 5]
so I want a code to give this result for mean difference of first neighbors:
d(1,1)=[(1-4)+(1-8)]/2, d(1,2)=[(4-1)+(4-5)+(4-10)]/3, d(2,2)=[(10-8)+(10-0)+(10-4)+(10-5)]/4 and etc. For second neighbors: dd(3,3)=[(20-2)+(20-9)+(20-5)+(20-18)/4].
thank you

답변 (1개)

Walter Roberson
Walter Roberson 2017년 10월 29일
mask = [0 1 0; 1 0 1; 0 1 0];
Ncount = conv2(ones(size(a)), mask, 'same');
d = double(a) - conv2(double(a), mask, 'same')./Ncount;
You can leave out the double() if you are sure that a will not be integer data type (images are usually integer data type.)
For second difference, use an appropriate larger mask such as
[0 0 1 0 0; 0 0 0 0 0; 1 0 0 0 1; 0 0 0 0 0; 0 0 1 0 0]
  댓글 수: 2
ichi
ichi 2017년 10월 30일
Thank you for the answer, I knew the conv2(a,mask,'same'), gives you the sum of the neighbors of each element, but this method is so good.
Walter Roberson
Walter Roberson 2017년 10월 30일
If the question is resolved, please Accept the answer.

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