# [Numpy-discussion] Array2 subset of array1

Eelco Hoogendoorn hoogendoorn.eelco at gmail.com
Tue Aug 5 12:59:41 EDT 2014

```ah yes, that may indeed be what you want. depending on your datatype, you
could access the underlying raw data as a string.

b.tostring() in a.tostring() sort of works; but isn't entirely safe, as you
may have false positive matches which arnt aligned to your datatype
using str.find in combination with dtype.itemsize could solve that problem;
though it isn't the most elegant solution id say. also note that you need
to check for identical datatypes and memory layout for this to guarantee
correct results.

On Tue, Aug 5, 2014 at 6:33 PM, Sebastian Berg <sebastian at sipsolutions.net>
wrote:

> On Di, 2014-08-05 at 14:58 +0200, Jurgens de Bruin wrote:
> > Hi,
> >
> > I am new to numpy so any help would be greatly appreciated.
> >
> > I have two arrays:
> >
> >     array1 = np.arange(1,100+1)
> >     array2 = np.arange(1,50+1)
> >
> > How can I calculate/determine if array2 is a subset of array1 (falls
> > within array 1)
> >
> > Something like : array2 in array1 = TRUE for the case above.
> >
>
> Just to be clear. You are looking for the whole of array1 (as a
> block/subarray) as far as I understand. And there is no obvious numpy
> way to do this. Depending on your array sizes, you could blow up the
> first array from (N,) to (N-M+1,M) and then check if any row matches
> completely. There may be better tricks available though, especially if
> array1 is large.
>
> - Sebastian
>
> > Thank
> > _______________________________________________
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> > NumPy-Discussion at scipy.org
> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
>
>
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