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

Marlin Rowley marlin_rowley@hotmail....
Wed Jul 9 15:34:08 CDT 2008


Thanks Chuck, but I wasn't quit clear with my question.
 
You answered exactly according to what I asked, but I failed to mention needing the dot product instead of just the product.
 
So, 
 
v dot A = v'
 
v'[0] = v[0]*A[0] + v[1]*A[1] + v[2]*A[2]
v'[1] = v[0]*A[3] + v[1]*A[4] + v[2]*A[5]
v'[2] = v[0]*A[6] + v[1]*A[7] + v[2]*A[8]
 
-M



Date: Wed, 9 Jul 2008 13:26:01 -0600From: charlesr.harris@gmail.comTo: numpy-discussion@scipy.orgSubject: Re: [Numpy-discussion] Multiplying every 3 elements by a vector?
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))*vYou might want to reshape the result to 1-D.Chuck 
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