Logical arrays as indices to arrays to convert elements to zero in MATLAB
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Logical arrays as indices to arrays to convert elements to zero in MATLAB
I am trying to convert some elements of a matrix to zeros depending on a logical array.
Suppose we have a random 5 x 5 matrix:
5 x 5
b =
0.0344 0.1869 0.7547 0.1190 0.2238
0.4387 0.4898 0.2760 0.4984 0.7513
0.3816 0.4456 0.6797 0.9597 0.2551
0.7655 0.6463 0.6551 0.3404 0.5060
0.7952 0.7094 0.1626 0.5853 0.6991
And I have an array of zeros and ones with the same dimension:
a =
0 1 1 0 0
1 0 1 1 0
1 1 0 1 1
0 1 1 0 1
0 0 1 1 0
Doing a(logical(b)) gives me the elements I am looking for, but in a vector form:
a(logical(b))
ans =
0.4387
0.3816
0.1869
0.4456
0.6463
0.7547
0.2760
0.6551
0.1626
0.4984
0.9597
0.5853
0.2551
0.5060
How can I get the following matrix instead?
0 0.1869 0.7547 0 0
0.4387 0 0.2760 0.4984 0.7513
0.3816 0.4456 0 0.9597 0.2551
0 0.6463 0.6551 0 0.5060
0 0 0.1626 0.5853 0
1 Answer
1
I just realized that there was an answer in another question.
Setting b(~logical(a)) = 0 works.
b(~logical(a)) = 0
(Just keeping this here because the question is phrased a bit differently.)
b(a == 0) = 0;
~logical(a)
You could also do an element-wise multiply
.*.– knedlsepp
Apr 1 '15 at 0:20
.*
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You can do
b(a == 0) = 0;to be even shorter. I would say this more expressly states what you want to do rather than using~logical(a).– rayryeng
Apr 1 '15 at 0:15