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Increase nonzero values without deleting zeros

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monmatlab
monmatlab on 12 Apr 2017
Commented: David J. Mack on 12 Apr 2017
I have a vector X.
X=[0 0 0 0 1 1 1 1 0 0 0 0 0 0 2 2 2 2 2 2 0 0 0 3 3 3 3 0 0 0 0 0 4 4 4]
I want to increase the values of the nonzero elements in vector X by 10 However, when I do this using the find function I end up just having a vector without the zeros.
Y=X((find(X~=0)))+10;
Y=[11 11 11 11 22 22 ... ]
Is there a way to do this without using a for loop?

  2 Comments

KSSV
KSSV on 12 Apr 2017
Where you want to place the non zeros numbers?
monmatlab
monmatlab on 12 Apr 2017
at their initial positions. I want to have the same vector , just with the nonzeros increased by ten

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Accepted Answer

David J. Mack
David J. Mack on 12 Apr 2017
Edited: David J. Mack on 12 Apr 2017
Hey monmatlab, simply use logical indexing:
Y = X;
isNonzero = X~=0;
Y(isNonzero) = 10*Y(isNonzero);
or the more compact inplace replacement:
X(X~=0) = 10*X(X~=0);
Greetings, David

  2 Comments

Adam
Adam on 12 Apr 2017
If this is what you actually want to do, with multiplication then you can just skip the logical part and use
X = X * 10
since multiplying by 0 is 0 anyway! I was under the impression you wanted to add 10, not multiply by it though.
David J. Mack
David J. Mack on 12 Apr 2017
Ah true, the OP stated to increase it... but it's the same idea anyway. Just replace the * by a +.

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More Answers (1)

Adam
Adam on 12 Apr 2017
X = ( X ~= 0 ) .* ( X + 10 );

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