[SciPy-user] How to use where
Alexander Borghgraef
alexander.borghgraef.rma@gmail....
Thu Aug 21 09:26:55 CDT 2008
On Thu, Aug 21, 2008 at 4:03 PM, Dave <dave.hirschfeld@gmail.com> wrote:
> In [1]: listofvectors = rand(100,2)
>
> In [2]: bound = array([0.5,0.8])
>
> In [3]: idx = all(listofvectors < bounds,axis=1)
>
> In [4]: inbounds = listofvectors[idx,:]
Neat. One less function call, seems like a good thing to me.
> I'm not sure of the utility of where - I tend to use boolean masks. Is there any
> reason one wouldn't use the code I posted above?
Can't see why not (please someone correct me if I'm wrong). After
playing with where a bit, my impression is that its main use is the
conditional replacement of elements, and not what I was trying to do
with it. For example:
a = arange(10)
> array([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
where( a > 4, 0, a ** 2)
> array([ 0, 1, 4, 9, 16, 25, 36, 0, 0, 0])
Anyway, thanks to everyone who responded!
--
Alex Borghgraef
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