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Increase nonzero values without deleting zeros

Asked by monmatlab on 12 Apr 2017
Latest activity Commented on by 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

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

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2 Answers

Answer by David J. Mack on 12 Apr 2017
Edited by David J. Mack on 12 Apr 2017
 Accepted Answer

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

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.
Ah true, the OP stated to increase it... but it's the same idea anyway. Just replace the * by a +.

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Answer by Adam
on 12 Apr 2017

X = ( X ~= 0 ) .* ( X + 10 );

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