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Re: set zero to multiple values in a matrix

From: Nicholas Jankowski
Subject: Re: set zero to multiple values in a matrix
Date: Sun, 30 Apr 2017 22:00:42 -0400

On Apr 30, 2017 6:52 PM, "BOKU" <> wrote:

i would like to know if there is a fast way to select some items of a indexed matrix?

this is not working in my case ?!

sel =

    [14   19   23   24   25   29]

lab is a 301x301 labeled matrix

   ans =  47

I want to do something like


do I really need to go through a loop for doing this?

no, but since you have indices off the ones you don't want, inverting may be easier using logical indexing. 


I'm guessing without octave open in front of me, but something like this should work.

idx = ones(size(lab))
idx(sel) = 0
lab(idx) = 0

That should create a logical index inverted from your linear index, and set all of those spots not in sel to 0. I can't remember if you need to cast idx as logical before the last line

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