CODEWITHSUNDEEP
matlabrandom
HCAI
HCAI

Reputation: 2263

Sampling from two vectors with randsample

I have 2 vectors (n and t) eg:

n  t
1  5
5  3
5  2
2  6
2  9

Once I sample from vector n through randsample(n,1), I want to sample from the vector t but only from the values corresponding to that same one in vector n.

eg. If I drew a value of 2 from n, I then want to draw the value 6 or 9 from t. But how do I tell matlab to do that?

Upvotes: 1

Views: 1494

Answers (2)

gevang
gevang

Reputation: 5014

Simple one-liner, assuming you have them stored in a Nx2 matrix 

nt = [
1  5;
5  3;
5  2;
2  6;
2  9];

meaning:

n = nt(:,1);
t = nt(:,2);

you can sample nSamples with replacement by randmonly indexing the matrix row-wise, i.e.: 

nSamples = 5;
keepSamples = nt(randi(length(nt),nSamples,1),:);

Upvotes: 1

Fantastic Mr Fox
Fantastic Mr Fox

Reputation: 33854

You could potentially do this:

out = t(n == randsample(n, 1))

This will create a filter based on whether n = its own random sample, ie if 

randsample(n, 1) = 2
(n == randsample(n, 1)) = [0
                           0
                           0
                           1
                           1]

and applying this to t ie:

 t(n == randsample(n, 1)) = [6
                             9]

which are the two corresponding values to 2 in n, but in t.

Hope this helps.

PS if you need just one value from t then you can randsample the output that this function gives you.

Upvotes: 2

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