A(B)=0 What is its meaning?

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zhenyu zeng
zhenyu zeng 2019-3-6
编辑： Torsten 2019-3-6
A=rand(5)
B=A>0.8
A(B)=0
Can you tell me what is A(B)=0 meaning?

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采纳的回答

Fangjun Jiang
Fangjun Jiang 2019-3-6
B is a logical index matrix. You can see the value is 1 (true) or 0 (false) wherever the corresponding value in A is greater than 0.8.
A(B)=0 means for all those places where B's value is true, set the corresponding value in A to 0.
Use this example to see it better.
A=magic(5)
B=A>10
A(B)=0
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显示 1更早的评论
Torsten
Torsten 2019-3-6
编辑：Torsten 2019-3-6
It's the same as if you ask why MATLAB loops if you write
for i=1:n
...
end
It's just MATLAB syntax.
Look up "Logical indexing":
https://blogs.mathworks.com/loren/2013/02/20/logical-indexing-multiple-conditions/
Fangjun Jiang
Fangjun Jiang 2019-3-6
It is a very efficient way for programming.

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更多回答（1 个）

Torsten
Torsten 2019-3-6
编辑：Torsten 2019-3-6
All numbers in the matrix A that are bigger than 0.8 are set to 0.

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