Assigning class +1/-1 to a 100x2 matrix
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Deepayan Bhadra
on 20 Feb 2018
Commented: Deepayan Bhadra
on 20 Feb 2018
I have a 100x2 matrix D. A scatter plot is attached. I have a 100x1 vector 'c'. If a point in D is to the left, I want to assign it as +1 and -1 otherwise. I know it sounds easy and I was trying this snippet:
if D(1:100,1)<mean(D(:,1)) c(:,1) = 1; else c(:,1) = -1; end
but it somehow doesn't do the job. I think we don't even need an if loop. Thanks for your comments.
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Accepted Answer
Cam Salzberger
on 20 Feb 2018
Hello Deepayan,
c = ones(size(D, 1), 1);
c(D(:, 1) > mean(D(:, 1))) = -1;
On the other hand, you've got some very nice clusters here, and this code depends on you having roughly equal number of points in each cluster. Rather than mean, it would probably make sense to use some form of cluster analysis to figure out where the clusters are, and which points belong to which. kmeans is one of the most common methods, and would probably suffice here.
-Cam
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