how to select random rows from a matrix?
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i have a matrix of size 10037 by 9.
please tell me how to select 1000 random rows from the matrix and save it as a mnew matrix in another variable.
thanks in advance.
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Answers (2)
Andrei Bobrov
on 7 Oct 2011
m = rand(10037,9);
k = randperm(10037);
mnew = m(k(1:1000),:);
7 Comments
Jan
on 24 Oct 2017
Or with the original order:
M = rand(10037,9);
k = randperm(10037, 1000);
Selected = M(k, :);
r = true(1,10037);
r(k) = false;
Remaining = M(r, :);
Richard Willey
on 7 Oct 2011
Statistics Toolbox includes a nice function called randsample
% Generate a matrix named foo
foo = randn(10000,2);
% draw 1000 random samples without replacement
index = randsample(1:length(foo), 1000);
bar = foo(index,:);
% draw 1000 random samples with replacement
index = randsample(1:length(foo), 1000, true);
bar = foo(index,:);
2 Comments
Peter Perkins
on 7 Oct 2011
If you happen to be using R2011b, and have access to the Statistics Toolbox, you can also use the new datasample function:
m = rand(10037,9);
mnew = datasample(m,1000);
This also allows you to sample with replacement, or with weights.
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