Can numpy do better than this?

Rustom Mody rustompmody at gmail.com
Fri Jan 9 02:45:34 CET 2015


On Friday, January 9, 2015 at 7:07:26 AM UTC+5:30, Ian wrote:
> On Thu, Jan 8, 2015 at 6:13 PM, Rustom Mody wrote:
> > With that I came up with the expression
> >
> > transpose(array([list(roll(mat[:,i],i,0)) for i in range(mat.shape[1])]))
> >
> > Not exactly pretty.
> > My hunch is it can be improved??...
> 
> Hmm, you could use the column_stack constructor to avoid having to
> transpose the array.
> 
> >>> np.column_stack(np.roll(mat[:,i],i,0) for i in range(mat.shape[1]))
> array([[ 1, 38, 33, 28, 23, 18],
>        [ 7,  2, 39, 34, 29, 24],
>        [13,  8,  3, 40, 35, 30],
>        [19, 14,  9,  4, 41, 36],
>        [25, 20, 15, 10,  5, 42],
>        [31, 26, 21, 16, 11,  6],
>        [37, 32, 27, 22, 17, 12]])

You are my sweetheart!

Removing Javaish-dot-noise:

column_stack(roll(mat[:,i],i,0) for i in range(mat.shape[1]))



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