Question about Indexing a function
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A = [-1 -2 0 1 2];
B = A(A<0);
What does A(A<0) mean exactly? and is there a way to do its function with an if statement? because I tried this and it did not work.
if A<0
B = A;
end
1 个评论
"What does A(A<0) mean exactly?"
A(A<0)
^^^ logical index
^^ ^ indexing into A
Basic MATLAB concepts, like how to use indexing, are explained here:
"and is there a way to do its function with an if statement?"
It could be done with a bit of effort, but that would be a very poor use of MATLAB.
采纳的回答
Dyuman Joshi
2021-4-27
编辑：Dyuman Joshi
2021-4-28
B = A(A<0) means to allocate all the elements of A which are less than zero to B.
In case you want to use if statement to obtain the same, use a for loop as follows -
B=[];
for i=1:numel(A)
if A(i)<0
B = [B A(i)];
end
end
However, using B = A(A<0) should be opted.
2 个评论
Mashari Alharbi
2021-4-27
Dyuman Joshi
2021-4-28
My bad, that is supposed to be A and not x. I have edited it.
更多回答（1 个）
Steven Lord
2021-4-27
2 个投票
That operation is logical indexing. Also see the "Indexing with Logical Values" section on this documentation page for more information.
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