[R] Find mean of values in three-dimensional array

[peter dalgaard]

> On 15 Jun 2016, at 19:37 , Nick Tulli <nick.tulli.95 at gmail.com> wrote:
> 
> Hey R-Help,
> 
> I've got a three dimensional array which I pulled from a netcdf file.
> The data in array are the humidity values of locations in the United
> States over a time period. The three dimensions are [longitude,
> latitude, days], 141x81x92. My goal is to find the mean value at each
> longitude/latitude over the 92 day period.
> 
> I could probably accomplish my goal by running a loop, but I'm sure
> that there is a much easier and more efficient way to accomplish the
> goal in R. Any suggestions?

Dunno about fast, but the canonical way is apply(A, c(1,2), mean)

E.g.

(A <- array(1:24,c(2,3,4)))
apply(A, c(1,2), mean)
apply(A, c(1,3), mean)

-pd

> 
> 
> Thanks guys.
> 
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-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
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Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com