How to save "for" loop outputs in cell array?
显示 更早的评论
I generated a code that gives all the 2x2 submatrices from a 10x7 matrix while keeping the order. I want to save each output (submatrix) as a matrix in a cell array to view it later. Here's my code:
Any help is appreciated!
clear
clc
matrix=rand(10,7)
[r, c]= size(matrix);
for s=1:r-1
for n=s+1:r-s
for j=1:c
for i=j+1:c
submatrix=matrix([s n],[j i])
end
end
end
end
采纳的回答
matrix=rand(10,7)
submatrix = {};
[r, c]= size(matrix);
for s=1:r-1
for n=s+1:r-s
for j=1:c
for i=j+1:c
submatrix{end+1}=matrix([s n],[j i]);
end
end
end
end
whos submatrix
celldisp(submatrix(1:5))
3 个评论
HN
2023-2-16
Walter Roberson
2023-2-16
Indexing at end+1 in an assignment is a common MATLAB idiom for appending data to the end of an array. end is a keyword in this context that converts to the index of the last element of the index. In the case of a single index being used (linear indexing) end converts to the number of elements currently in the array. So assigning to submatrix{end+1} is a more compact way of assigning to submatrix{numel(submatrix)+1} which is assigning to one past the current end of the array.
It saves having to write something like
submatrix = [submatrix, {matrix([s n],[j i])}];
Although the language model is such that assigning one past the end of an array "should" be the same as overwriting the variable with the output of explicitly creating an appended list like the above, it is not necessarily the same internally. The MATLAB memory allocation routines use fixed sized blocks for small arrays, and those fixed sized blocks might have room to extend the array in-place without allocating more memory, so for efficiency purposes assigning to {end+1} has the potential to be faster.
HN
2023-2-16
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