[Numpy-discussion] help vectorizing something
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. Thanks to any one of you vectorization gurus that has any ideas. Mathew ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] help vectorizing something
On Fri, Oct 24, 2008 at 3:48 PM, Mathew Yeates [EMAIL PROTECTED] 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 ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] help vectorizing something
h. 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 [EMAIL PROTECTED] wrote: On Fri, Oct 24, 2008 at 3:48 PM, Mathew Yeates [EMAIL PROTECTED]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 ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] help vectorizing something
On Fri, Oct 24, 2008 at 4:23 PM, Mathew Yeates [EMAIL PROTECTED] wrote: h. 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] Because b isn't a subset of a. You can get around this by counting the number, i.e., cnt = searchsorted(a,b, side='right') - seachsorted(a, b, side='left') so that In [1]: a = array([ 1, 2, 3, 7, 10]) In [2]: b = array([ 1, 2, 3, 8, 10]) In [3]: il = searchsorted(a, b, side='left') In [4]: ir = searchsorted(a, b, side='right') In [5]: compress(ir - il, il) Out[5]: array([0, 1, 2, 4]) Chuck ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
