MATLAB: How to find which postions in a vector has negative values and output them

vector

i have a vector and need to find the postions which has negative values

Say your vector is A:

idx=find(A<0)
ANeg=A(idx)

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.

s=sign(A)
ipositif=sum(s(:)==1)
inegatif=sum(s(:)==-1)