[Numpy-discussion] newbie question - summing a list of arrays

Chris Withers chris@simplistix.co...
Tue Mar 18 10:39:31 CDT 2008


Alan G Isaac wrote:
> On Tue, 18 Mar 2008, Chris Withers apparently wrote:
>> Say I have an aribtary number of arrays:
>> arrays = [array([1,2,3]),array([4,5,6]),array([7,8,9])] 
>> How can I sum these all together? 
> 
> Try N.sum(arrays,axis=0).

I assume N here is:

import numpy as N?

Yep, it is... and that works exactly as I expect.

Where are the docs for sum? Having had the book turn up as a massive PDF 
with a poor index/toc, I'm finding it just as difficult to navigate as 
the online docs :-(
(I, like most people on this list I'd guess, sadly don't have the time 
to sit and read the whole book cover-to-cover to extract the 10-20% I 
need to know :-S)

> But must they be in a list?
> An array of arrays (i.e., 2d array) is easy to sum.

Actually, I'm using a dict of arrays:

data = {
  'series1':array([1,2,3]),
  'series2':array([1,4,6]),
   'date':array([datetime(...),datetime(...),datetime(...)]),
  }

If that gives the idea?

Is there perhaps a better way to store these series?
(I'm a numpy newbie, I've skimmed the tutorial and it doesn't appear to 
help here)

cheers,

Chris

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