[Numpy-discussion] Multiplying every 3 elements by a vector?

Charles R Harris charlesr.harris@gmail....
Wed Jul 9 14:26:01 CDT 2008


On Wed, Jul 9, 2008 at 1:16 PM, Marlin Rowley <marlin_rowley@hotmail.com>
wrote:

> All:
>
> I'm trying to take a constant vector:
>
>  v = (0.122169, 0.61516, 0.262671)
>
> and multiply those values by every 3 components in an array of length N:
>
> A = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ....]
>
> So what I want is:
>
> v[0]*A[0]
> v[1]*A[1]
> v[2]*A[2]
> v[0]*A[3]
> v[1]*A[4]
> v[2]*A[5]
> v[0]*A[6]
>
> ...
>
> How do I do this with one command in numPy?
>
>

If the length of A is divisible by 3:

A.reshape((-1,3))*v

You might want to reshape the result to 1-D.

Chuck
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