# [NumPy-Tickets] [NumPy] #1995: DOC: numpy.correlate() docstring is wrong

NumPy Trac numpy-tickets@scipy....
Sat Jul 21 14:49:17 CDT 2012

```#1995: DOC: numpy.correlate() docstring is wrong
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Reporter:  O.C.        |       Owner:  somebody
Type:  defect      |      Status:  needs_review
Priority:  normal      |   Milestone:  Unscheduled
Component:  numpy.core  |     Version:  1.5.1
Keywords:              |
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Changes (by O.C.):

* status:  new => needs_review

Comment:

I provide an example to confirm what I wrote above:
{{{
a, v = arange(5), arange(3)
z = correlate(a,v)            # array([ 5,  8, 11])
z[1]                          # 8

# With the formula described in the docstring, z[k] = sum_n a[n] *
conj(v[n+k]),
# we have z[1] = sum_n a[n] * conj(v[n+1])
sum(a[:2] * v[1:])
2                         # does not match the output of correlate(a,v)

# With the formula I give above, z[k] = sum_n a[n] * conj(v[n-k]),
# we have z[1] = sum_n a[n] * conj(v[n-1])
sum(a[1:4] * v)
8                         # identical to the output of correlate(a,v)
}}}
The patch is just a change in the docstring.

--
Ticket URL: <http://projects.scipy.org/numpy/ticket/1995#comment:1>
NumPy <http://projects.scipy.org/numpy>
My example project
```