matrix variable problem in matlab

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

Answer 1

[Henry Tran]

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.

[javad hemati]

Thank you <3

[javad hemati]

about the b(c)=0, what do you mean by '' which are along the 1 of c ''. I didn't catch that part

[the cyclist]

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.

[javad hemati]

Thank you. got it now

Answer 2

[the cyclist]

This documentation about indexing with logical values might help you understand.

[javad hemati]

Thanks <3