# [Numpy-discussion] help vectorizing something

Mathew Yeates mat.yeates@gmail....
Fri Oct 24 17:23:16 CDT 2008

```hmmmm. I don't understand the result.

If
a=array([ 1,  2,  3,  7, 10]) and b=array([ 1,  2,  3,  8, 10])

I want to get the result [0,1,2,4] but[searchsorted(a,b) produces
[0,1,2,4,4] ?? and searchsorted(b,a) produces [0,1,2,3,4]

??
Mathew

On Fri, Oct 24, 2008 at 3:12 PM, Charles R Harris <charlesr.harris@gmail.com
> wrote:

>
>
> On Fri, Oct 24, 2008 at 3:48 PM, Mathew Yeates <mat.yeates@gmail.com>wrote:
>
>> Hi
>> I  have 2 vectors A and B. For each value in A I want to find the location
>> in B of the same value. Both A and B have unique elements.
>>
>> Of course I could something like
>> For each index of A:
>>        v =A[index]
>>        location = numpy.where(B == v)
>>
>> But I have very large lists and it will take too long.
>>
>
> In [1]: A = array([1,2,3])
>
> In [2]: B = array([5,1,3,0,2,4])
>
> In [3]: i = B.argsort()
>
> In [4]: Bsorted = B[i]
>
> In [5]: indices = i[searchsorted(Bsorted,A)]
>
> In [6]: indices
> Out[6]: array([1, 4, 2])
>
> Chuck
>
>
>
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