Number of Elements Between 2 Elements in a matrix.

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s.v.
s.v. 2018년 2월 2일
답변: Star Strider 2018년 2월 2일
Say I have a 3x5 matrix of zeros.
M = zeros(3,5)
00000
00000
00000
I change two elements in the matrix so the following happens.
M(1,3) = 1
M(3,3) = 2
00100
00000
00200
How do I count the number of elements between "1" and "2"?
Like below, it would be 11 elements within the brackets.
00[100
00000
002]00
As little lines of code as possible would be appreciated! Thank you.

채택된 답변

Star Strider
Star Strider 2018년 2월 2일
MATLAB uses column-major ordering, so it ‘counts’ elements column-wise, and it is necessary to transpose ‘M’ to do what you want.
M = zeros(3,5);
M(1,3) = 1;
M(3,3) = 2;
idx = find(M');
Result = diff(idx)+1
Result =
11
These can be combined into a one-line assignment:
Result = diff(find(M'))+1
It is necessary to add 1, because diff does not take into account the initial or final element when it does its subtraction.

추가 답변 (1개)

James Tursa
James Tursa 2018년 2월 2일
편집: James Tursa 2018년 2월 2일
Assuming the matrix has exactly two nonzero entries:
M = your matrix
f = find(M'); % Transpose to get the row data into column order
result = f(2) - f(1) + 1;
If you can't guarantee that there are exactly two nonzero entries, then you will have to add in appropriate checks etc and tell us what you would want for a result in that case.

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