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From: Patrick on 9 May 2010 19:58
I have a number of 2-D arrays (13 x 9 double) and I would like to compute the element-by-element means, resulting in a 13 x 9 matrix of mean values. Seems like this should be a simple operation, analogous to multiplication (.*), but I've been unable to find a function that helps.

My example more specifically: I have 31 13 x 9 matrices, each representing a day of a particular month, e.g. 'Dec01', 'Dec02', 'Dec03', etc. I would like to get the average monthly value of each element, e.g. 'Dec_avg', also a 13 x 9 matrix.

Suggestions? Do I need to create a 3-D array, with a dimension representing the day?
Thanks.
From: Tombo H on 9 May 2010 20:12
Didn't this work:

averageMatrix = (1/31) *
(Dec01+Dec02+Dec03+Dec04+Dec05+Dec06+Dec07+Dec08+Dec09+Dec10+Dec11+Dec12+Dec13+Dec14+Dec15+Dec16+Dec17+Dec18+Dec19+Dec20+Dec21+Dec22+Dec23+Dec24+Dec25+Dec26+Dec27+Dec28+Dec29+Dec30+Dec31);

where each Decnn is a 13x9 double matrix?
From: John D'Errico on 9 May 2010 20:29
"Patrick " <gallagjo(a)interchange.ubc.ca> wrote in message <hs7i6c$b1v$1(a)fred.mathworks.com>...
> I have a number of 2-D arrays (13 x 9 double) and I would like to compute the element-by-element means, resulting in a 13 x 9 matrix of mean values. Seems like this should be a simple operation, analogous to multiplication (.*), but I've been unable to find a function that helps.
>
> My example more specifically: I have 31 13 x 9 matrices, each representing a day of a particular month, e.g. 'Dec01', 'Dec02', 'Dec03', etc. I would like to get the average monthly value of each element, e.g. 'Dec_avg', also a 13 x 9 matrix.
>
> Suggestions? Do I need to create a 3-D array, with a dimension representing the day?
> Thanks.

Since that would be by far the most logical way to
do it, why not? Naming separate arrays like that, with
distinct numbers is a terrible approach. It forces you
to do silly things, when a single call to mean would
have sufficed otherwise.

John
From: Patrick on 9 May 2010 20:36
Tombo H <tombo.hayworth(a)gmail.com> wrote in message <69e88147-ce61-4284-acac-48465a9012fd(a)k19g2000yqm.googlegroups.com>...
> Didn't this work:
>
> averageMatrix = (1/31) *
> (Dec01+Dec02+Dec03+Dec04+Dec05+Dec06+Dec07+Dec08+Dec09+Dec10+Dec11+Dec12+Dec13+Dec14+Dec15+Dec16+Dec17+Dec18+Dec19+Dec20+Dec21+Dec22+Dec23+Dec24+Dec25+Dec26+Dec27+Dec28+Dec29+Dec30+Dec31);
>
> where each Decnn is a 13x9 double matrix?

Yes, although the command string could get quite long (I actually want to average more than a month's worth of days), this appears to be a simple solution that works. Thanks for the quick response.
Patrick
From: Steven Lord on 9 May 2010 21:39

"Patrick " <gallagjo(a)interchange.ubc.ca> wrote in message
news:hs7kdj$2j3$1(a)fred.mathworks.com...
> Tombo H <tombo.hayworth(a)gmail.com> wrote in message
> <69e88147-ce61-4284-acac-48465a9012fd(a)k19g2000yqm.googlegroups.com>...
>> Didn't this work:
>>
>> averageMatrix = (1/31) *
>> (Dec01+Dec02+Dec03+Dec04+Dec05+Dec06+Dec07+Dec08+Dec09+Dec10+Dec11+Dec12+Dec13+Dec14+Dec15+Dec16+Dec17+Dec18+Dec19+Dec20+Dec21+Dec22+Dec23+Dec24+Dec25+Dec26+Dec27+Dec28+Dec29+Dec30+Dec31);
>>
>> where each Decnn is a 13x9 double matrix?
>
> Yes, although the command string could get quite long (I actually want to
> average more than a month's worth of days), this appears to be a simple
> solution that works. Thanks for the quick response.

In that case, don't create variables like that. Instead, since they're all
the same size, store them as "pages" of a 3D array.

dataForDecember = zeros(13, 9, 31)

Then use MEAN specifying the dimension over which you want to take the mean.

--
Steve Lord
slord(a)mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ


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