Display only positive values

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Kat 2019-9-28

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评论： Star Strider 2019-9-28

Hello. I am trying to display only the positive values of a vector by using the find function to find where the negative values are first and then displaying only the positive values. I have tried using i = find(vector<0) but I don't know how to only delete the negative values using the find function to display only the positive values. Thanks.

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Answer 1

Star Strider 2019-9-28

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Yolu can simply use logical indexing for this, find is not absolutely necessary.

However, if you want to use find, assign its output to a variable:

idx = find(vector>0);
PosVals = vector(idx);

Testing for the negative values and then eliminating them requires an extra step:

idx = find(vector<0);
posidx = setdiff((1:numel(vector)), idx);
PosVals = vector(posidx)

Experiment to get different results.

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Kat 2019-9-28

Is there a way to do that without using any other built-in functions? Thanks.

Star Strider 2019-9-28

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Yes. Just test for positive values and return those indices. If you want to test for negative velues, use logical indexing and the logical negation (~) operator:

Lneg = vector < 0;                                      % Logical Vector Of Elements < 0
Lpos = ~Lneg;                                           % Logical Vector Of Elements >= 0

Then use find with those if you want to.

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