R help - Jan 2010 - Looping multiple dimensions

Dear all,

I have 30 arrays, each with dimensions 720,360,12. The naming format for each of
these 30 objects is: mrunoff_5221, mrunoff_5222... mrunoff_5250.


For example:
> str(mrunoff_5221)
? num [1:720, 1:360, 1:12] NA NA NA NA NA NA NA NA NA NA ...? (the initial
NA's are nothing to worry about)


I am looking for a way by which I can extract each of the third dimension of
these grids (1:12) in turn, along with the first and second dimensions, to
create new objects in the following style:


#2071
mrunoff_207101 <- mrunoff_5221[,,1]
mrunoff_207102 <- mrunoff_5221[,,2]
mrunoff_207103 <- mrunoff_5221[,,3]
mrunoff_207104 <- mrunoff_5221[,,4]
mrunoff_207105 <- mrunoff_5221[,,5]?? ...(etc. - up to [,,12])

#2072
mrunoff_207201 <- mrunoff_5222[,,1]
mrunoff_207202 <- mrunoff_5222[,,2]
mrunoff_207203 <- mrunoff_5222[,,3]
mrunoff_207204 <- mrunoff_5222[,,4]
mrunoff_207205 <- mrunoff_5222[,,5]? ...(etc. - up to [,,12]) and mrunoff_
continues to 2100 and 5250 respectively.


Clearly, this is a cumbersome and non-sustainable way to proceed! There will be
360 new objects in total, and I imagine that there must be a more effective way
of achieving this, either via a loop or, possibly, one of the 'apply'
functions. Yet my attempts to date have so far resulted in... well, a complete
mess!

If anyone has any suggestions as to a more efficient means of achieving this,
then I'd be very grateful to hear them.

Many thanks,

Steve

 		 	   		  
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I would suggest that you use a 'list' for the data.  Something like
this should work:

objs <- grep("^mrunoff_", ls(), values=TRUE)  # get the names of
the objects
result <- lapply(objs, function(.obj){
    .obj <- get(.obj)  # get the value
    lapply(1:12, function(. iter)  .obj[,, .iter])
})



On Fri, Jan 22, 2010 at 11:32 AM, Steve Murray <smurray444 at hotmail.com>
wrote:
>
> Dear all,
>
> I have 30 arrays, each with dimensions 720,360,12. The naming format for
each of these 30 objects is: mrunoff_5221, mrunoff_5222... mrunoff_5250.
>
>
> For example:
>> str(mrunoff_5221)
> ? num [1:720, 1:360, 1:12] NA NA NA NA NA NA NA NA NA NA ...? (the initial
NA's are nothing to worry about)
>
>
> I am looking for a way by which I can extract each of the third dimension
of these grids (1:12) in turn, along with the first and second dimensions, to
create new objects in the following style:
>
>
> #2071
> mrunoff_207101 <- mrunoff_5221[,,1]
> mrunoff_207102 <- mrunoff_5221[,,2]
> mrunoff_207103 <- mrunoff_5221[,,3]
> mrunoff_207104 <- mrunoff_5221[,,4]
> mrunoff_207105 <- mrunoff_5221[,,5]?? ...(etc. - up to [,,12])
>
> #2072
> mrunoff_207201 <- mrunoff_5222[,,1]
> mrunoff_207202 <- mrunoff_5222[,,2]
> mrunoff_207203 <- mrunoff_5222[,,3]
> mrunoff_207204 <- mrunoff_5222[,,4]
> mrunoff_207205 <- mrunoff_5222[,,5]? ...(etc. - up to [,,12]) and
mrunoff_ continues to 2100 and 5250 respectively.
>
>
> Clearly, this is a cumbersome and non-sustainable way to proceed! There
will be 360 new objects in total, and I imagine that there must be a more
effective way of achieving this, either via a loop or, possibly, one of the
'apply' functions. Yet my attempts to date have so far resulted in...
well, a complete mess!
>
> If anyone has any suggestions as to a more efficient means of achieving
this, then I'd be very grateful to hear them.
>
> Many thanks,
>
> Steve
>
>
> _________________________________________________________________
> Tell us your greatest, weirdest and funniest Hotmail stories
>
> ______________________________________________
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>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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