# [Numpy-discussion] mean of two or more arrays while ignoring a specific value

Chris Colbert sccolbert@gmail....
Tue Jul 14 14:36:11 CDT 2009

```index with a boolean array?

>>> import numpy as np
>>> a = np.array([3, 3, 3, 4, 4, 4])
>>> a
array([3, 3, 3, 4, 4, 4])
>>> np.average(a)
3.5
>>> b = a != 3
>>> b
array([False, False, False,  True,  True,  True], dtype=bool)
>>> np.average(a[b])
4.0
>>>

On Tue, Jul 14, 2009 at 3:33 PM, Greg Fiske<gfiske@whrc.org> wrote:
> Dear list,
>
>
>
> I’m learning to work with numpy arrays.  Can somebody explain how to get the
> average of two separate arrays while ignoring a user defined value in one
> array?
>
>
>
> For example:
>
>>>>a = numpy.array([1,5,4,99])
>
>>>>b = numpy.array([3,7,2,8])
>
>
>
> Ignoring the value 99, the result should be an array like c= ([2,6,3,8])
>
>
>
>
>
>
> Greg
>
>
>
>
>
> Greg Fiske
>
> Research Associate/GIS Manager
>
> The Woods Hole Research Center
>
>
> Falmouth MA, 02540
>
> 508-540-9900x139
>
> gfiske@whrc.org
>
> http://whrc.org
>
>
>
> _______________________________________________
> NumPy-Discussion mailing list
> NumPy-Discussion@scipy.org
> http://mail.scipy.org/mailman/listinfo/numpy-discussion
>
>
```