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pythonlistnumpyshuffle
Cheshie
Cheshie

Reputation: 2837

How to shuffle a matrix and an array accordingly

Suppose I have an mXd matrix called X, and an mX1 array called Y (using numpy). The rows of X correspond to the rows of Y.

Now suppose I need to shuffle the data (the rows) in X. I used:

random.shuffle(X)

Is there a way for me to keep track of the way X has been shuffled, so I could shuffle Y accordingly?

Thank you :)

Upvotes: 0

Views: 771

Answers (1)

mdml
mdml

Reputation: 22882

You can use numpy.random.permutation to create a permuted list of indices, and then shuffle both X and Yusing those indices:

>>> import numpy
>>> m = 10
>>> X = numpy.random.rand(m, m)
>>> Y = numpy.random.rand(m)
>>> indices = numpy.random.permutation(m)
>>> indices
array([4, 7, 6, 9, 0, 3, 1, 2, 8, 5])
>>> Y
array([ 0.53867012,  0.6700051 ,  0.06199551,  0.51248468,  0.4990566 ,
        0.81435935,  0.16030748,  0.96252029,  0.44897724,  0.98062564])
>>> Y = Y[indices]
>>> Y
array([ 0.4990566 ,  0.96252029,  0.16030748,  0.98062564,  0.53867012,
        0.51248468,  0.6700051 ,  0.06199551,  0.44897724,  0.81435935])
>>> X = X[indices, :]

Upvotes: 2

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