[Numpy-discussion] Quick array value assignment based on common values
Gökhan Sever
gokhansever@gmail....
Wed Aug 4 20:00:37 CDT 2010
On Wed, Aug 4, 2010 at 6:59 PM, <PHobson@geosyntec.com> wrote:
> Hey folks,
>
> I've one array, x, that you could define as follows:
> [[1, 2.25],
> [2, 2.50],
> [3, 2.25],
> [4, 0.00],
> [8, 0.00],
> [9, 2.75]]
>
> Then my second array, y, is:
> [[1, 0.00],
> [2, 0.00],
> [3, 0.00],
> [4, 0.00],
> [5, 0.00],
> [6, 0.00],
> [7, 0.00],
> [8, 0.00],
> [9, 0.00],
> [10,0.00]]
>
> Is there a concise, Numpythonic way to copy the values of x[:,1] over to
> y[:,1] where x[:,0] = y[:,0]? Resulting in, z:
> [[1, 2.25],
> [2, 2.50],
> [3, 2.25],
> [4, 0.00],
> [5, 0.00],
> [6, 0.00],
> [7, 0.00],
> [8, 0.00],
> [9, 2.75],
> [10,0.00]]
>
> My current task has len(x) = 25000 and len(y) = 350000 and looping through
> is quite slow unfortunately.
>
> Many thanks,
> -paul
>
>
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>
My simplest approach would be:
y[x[:0]-1] = x
# Providing the arrays are nicely ordered and 1st column x is all integer.
--
Gökhan
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