MATLAB Central Newsreader - averaging data series

averaging data series

Ben — Mon, 23 Jun 2008 18:33:02 -0400

I have a quick question.

I have data listed in 10 minute intervals and I was
wondering how to average it, so that the data is now in 30
minute intervals. The data is already in a .mat file. I
need to transform it into a different average. There is
about 10 years worth of data so I can't do it individually
or using vector indexing.

Thanks.

Re: averaging data series

roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson) — Mon, 23 Jun 2008 18:35:54 -0400

In article <g3oq8u$c88$1@fred.mathworks.com>, Ben <bburrou2@uiuc.edu> wrote:

>I have data listed in 10 minute intervals and I was
>wondering how to average it, so that the data is now in 30
>minute intervals.

decimate() would sound appropriate.
--
  "Beauty, like all other qualities presented to human experience,
  is relative; and the definition of it becomes unmeaning and
  useless in proportion to its abstractness." -- Walter Pater

Re: averaging data series

AMK — Tue, 22 Jul 2008 21:51:58 -0400

This looks like a convenient function, but I am unable to make it work.

>> y = decimate(data(:,1),2)
??? Undefined function or method 'decimate' for input arguments of type 'double'.

Where data(:,1) = dt = datenum(y1(:,3), y1(:,4), y1(:,5), y1(:,6), y1(:,7), 0) are 1 hour data.

Does this run from the base matlab command prompt?

Re: averaging data series

roberson@ibd.nrc-cnrc.gc.ca (Walter Roberson) — Tue, 22 Jul 2008 23:04:25 -0400

In article <26631652.1216763549409.JavaMail.jakarta@nitrogen.mathforum.org>,
AMK <kennaster@gmail.com> wrote:
>This looks like a convenient function, but I am unable to make it work.

>>> y = decimate(data(:,1),2)
>??? Undefined function or method 'decimate' for input arguments of type 'double'.

Sorry, it appears to be part of the signal processing toolbox.
--
"You can't hit what you can't see." -- Walter "The Big Train" Johnson

Re: averaging data series

Roger Stafford — Wed, 23 Jul 2008 00:32:02 -0400

"Ben " <bburrou2@uiuc.edu> wrote in message <g3oq8u$c88
$1@fred.mathworks.com>...
> I have a quick question.
>
> I have data listed in 10 minute intervals and I was
> wondering how to average it, so that the data is now in 30
> minute intervals. The data is already in a .mat file. I
> need to transform it into a different average. There is
> about 10 years worth of data so I can't do it individually
> or using vector indexing.
>
> Thanks.

If the number of successive 10-minute entries is a multiple of three, you can
do the following. Let x be a column vector of the data.

x2 = mean(reshape(x,[],3),2);

Now x2 is a column vector of one third as many 30-minute averages.

Roger Stafford

Re: averaging data series

AMK — Wed, 23 Jul 2008 01:31:25 -0400

My data aren't in that format. In fact, I have 1 minute and fifteen minute data that need to be aggregated into 30 minute averages. It seems like this might be better accomplished outside of Matlab and then brought in?