[Numpy-discussion] Indexing question

[Robert Kern]

On Thu, May 20, 2021 at 9:47 AM Neal Becker <ndbecker2 at gmail.com> wrote:

> This seems like something that can be done with indexing, but I
> haven't found the solution.
>
> out is a 2D array is initialized to zeros.  x is a 1D array whose
> values correspond to the columns of out.  For each row in out, set
> out[row,x[row]] = 1.  Here is working code:
> def orthogonal_mod (x, nbits):
>     out = np.zeros ((len(x), 1<<nbits), dtype=complex)
>     for e in range (len (x)):
>         out[e,x[e]] = 1
>     return out
>
> Any idea to do this without an explicit python loop?
>


i = np.arange(len(x))
j = x[i]
out[i, j] = 1

-- 
Robert Kern
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