[R] spinning and flipping arrays

Bill Rising brising at louisville.edu
Mon May 26 21:13:01 CEST 2003

On 5/26/2003 15:05, Spencer Graves wrote

>	  I know of no single function to do this;  perhaps someone else does. 
>  I don't have time to write and debug functions to do this myself, but 
>it should be easy enough to write functions like the following:
>flip3 <-
>   n3 <- dim(x)[3]
>   x[,,n3:1]
>spin3 <-
>function(x, k=1){
>   n3 <- dim(x)[3]
>   x[,,1+(((1+k):(n3+k))%%n3)]

These are pretty much what I'd figured out...

>With a little more work, I could generate functions that would do this 
>for any dimension of arrays with any number of dimensions.  To do that, 
>I might have to compute S-Plus commands using "cmd <- paste(...)" and 
>then execute them using "eval(parse(text=cmd))".

This last piece is what I think I needed. I had been trying to just put 
/argument/ to the "[" command together, instead of putting together the 
entire command.

Thanks for the tip. I'll keep working on it.

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