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pythonnumpyrotation
uniQ
uniQ

Reputation: 125

Numpy Row by Row Rotation

I have a 500x2 numpy array and a 2x2 rotation array. I would like to rotate each row of the array using the rotation array.

I have tried 

R.dot(A)

where R is the rotation array and A is the 500x2 array. But get the following error:

shapes (2,2) and (500,2) not aligned: 2 (dim 1) != 500 (dim 0)

Is there a way to do this row by row?

Thanks

Upvotes: 0

Views: 214

Answers (1)

Danny Rivers
Danny Rivers

Reputation: 46

For matrix multiplication, you need the inner dimensions to match (m by n and n by k). You're trying to multiply a 2 by 2 matrix with a 500 by 2 matrix - you need to take the transpose of the second matrix. Try

R.dot(A.transpose())

The columns of the result should be your rotated vectors. If you need it to be in row form, you can take the transpose again:

R.dot(A.transpose()).transpose()

Upvotes: 2

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