[MATRIX-SIG] reverse of take?

[Konrad Hinsen]

> Can you index a multi-dimensional array with a one-dimensional array? In
> other words does arraytype[range(10)] refer to the first 10 elements of
> the array? I think this would be doable using other more verbose methods,
> but this is a simple way to spell this.

This issue is already settled. Obviously, array[range(10)] should be
the same as array[:10], right? And that expression is equivalent to
array[:10, ...].

To get the first ten elements, use ravel(array)[:10].

> Can you index a one-dimensional array with a multi-dimensional array? In
> languages which provide this, this usually returns a value with the same
> shape as the matrix and the values corresponding to the value in the vector
> with that index. This is really nice for image processing - for example
> palette remapping. You can get this by applying a function, but that is
> usually a lot slower.

I see no reason why this shouldn't be allowed in NumPy.

> 1. A function which returns the permutation which would put the elements of
>    a 1-d array in order. In APL this is called 'upgrade' and in S it is called
>    'order'. A quick illustration of the use of this is computing the ranks

And in NumPy it's called argsort!
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Konrad Hinsen                          | E-Mail: hinsen@ibs.ibs.fr
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