[SciPy-user] extract array elements whis where() output

[Steve Schmerler]

First of all: what's better (a) post this only on the numpy list (b)
only on the scipy list (I think many scipy users may find the answer to
questions like this one interesting) or (c) post on both.

I can't extract elements from array x with a mask array of indices but
x.take (Numeric style works). I'm sure that I have done such things
before .... and they worked.

In [58]: x
Out[58]: array([0, 0, 1, 2, 3, 0, 0, 9])

In [59]: mask=where(x!=0.0)[0]

In [60]: mask
Out[60]: array([2, 3, 4, 7])

In [61]: x.take(mask)
Out[61]: array([1, 2, 3, 9])

In [62]: x(mask)
---------------------------------------------------------------------------
exceptions.TypeError Traceback (most
recent call last)

/home/elcorto/ode_testdata/<ipython console>

TypeError: 'numpy.ndarray' object is not callable

In [63]: numpy.__version__
Out[63]: '0.9.9.2612'

cheers,
steve

[Robert Kern]

Post by Steve Schmerler
First of all: what's better (a) post this only on the numpy list (b)
only on the scipy list (I think many scipy users may find the answer to
questions like this one interesting) or (c) post on both.

Probably (a). (c) should never be done except for single-shot announcements.

Post by Steve Schmerler
I can't extract elements from array x with a mask array of indices but
x.take (Numeric style works). I'm sure that I have done such things
before .... and they worked.
In [58]: x
Out[58]: array([0, 0, 1, 2, 3, 0, 0, 9])
In [59]: mask=where(x!=0.0)[0]
In [60]: mask
Out[60]: array([2, 3, 4, 7])
In [61]: x.take(mask)
Out[61]: array([1, 2, 3, 9])
In [62]: x(mask)
---------------------------------------------------------------------------
exceptions.TypeError Traceback (most
recent call last)
/home/elcorto/ode_testdata/<ipython console>
TypeError: 'numpy.ndarray' object is not callable

You meant x[mask], not x(mask).

[Steve Schmerler]

Post by Robert Kern
You meant x[mask], not x(mask).

Of course .... :) Thanks.

cheers,
steve

[Johannes Loehnert]

Hi,

Post by Steve Schmerler
In [62]: x(mask)

try x[mask]

Johannes