matrix variable problem in matlab

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javad hemati
javad hemati 2020-12-10
评论： javad hemati 2020-12-10
I have been assigned to run these codes and report what are they for. I'm good up to the 8th line. After that i'm lost and don't know what the last 3 lines do. I'll appreciate it if someone help me and explain what they do.
Thanks
a=rand(5);
b=a;
m=size(a,2);
x=1:m;
y=1:m;
xx=x'*ones(1,m);
yy=(y'*ones(1,m))';
c=xx==yy;
b(c)=0
c=xx.^2>yy;
a(c)=0

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采纳的回答

Henry Tran
Henry Tran 2020-12-10
编辑：Henry Tran 2020-12-10
Hi,
b(c)=0 %sets all values of b to 0, which are along the 1 of c
c=xx.^2>yy; %checks if the value of "xx.^2" is greater than the values in yy. If it is true then it returns as 1.
a(c)=0 --> %same principle as b(c)=0
I hope it answers your question.
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the cyclist
the cyclist 2020-12-10
I found the phrasing confusing, too. Here is an example. Suppose b and c are
b = [2 3 5 7 11]
c = [1 0 1 1 0];
Then b(c) will be
[2 5 7]
In other words, b(c) picks out the elements of b where c is equal to 1.

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the cyclist
the cyclist 2020-12-10
This documentation about indexing with logical values might help you understand.

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