[Numpy-discussion] yet another indexing question
Fri Oct 14 08:51:38 CDT 2011
Le vendredi 14 octobre 2011 à 08:04 -0400, Neal Becker a écrit :
> suppose I have:
> In : u
> array([[0, 1, 2, 3, 4],
> [5, 6, 7, 8, 9]])
> And I have a vector v:
> v = np.array ((0,1,0,1,0))
> I want to form an output vector which selects items from u where v is the index
> of the row of u to be selected.
> In the above example, I want:
> w = [0,6,2,8,4]
> I can't seem to find a syntax that does this.
> Now, more importantly, I need the result to be a reference to the original array
> (not a copy), because I'm going to use it on the LHS of an assignment. Is this
What about np.where?
w = np.where(v, u, u)
if you may want to have more than two options (more than two lines for
u), then np.choose may be more appropriate
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