R help - Apr 2007 - Inflate/Expand/Resize an array

Gudday,

I've had a good look everywhere trying to figure out how to do this, but
I'm afraid I can seem to find an answer anywhere - maybe its because I'm
not using the right terms, or maybe its because I'm a dummy. But
unfortunately, I am not completely and utterly stuck. Here's the
problem:

I have two large, six dimensional arrays that I would like to add
together. Lets call them f and m. Their dimensions are respectively:
> dim(f)
[1] 10  25  1  1  1 14
> dim(m)
[1] 10 1 1 1 1 14

You can see that they're pretty close in size, but not identical. What I
would like to do is expand or inflate m along its second dimension so
that it ends up with dimension 10 25 1 1 1 14, so that I can then add
the two together - the new values created along that second dimension
would simply be copies of the first value..

What's the fastest way to do this? Is there a dedicated function?
Ideally I envisage something that you feed the input array, and the
desired dimensions, and it does the rest for you. Please also bear in
mind that this is a specific problem - the more general case is where I
don't know which dimensions are "out of shape", so to speak...

I hope that's clear, and that someone can me out here...

Cheers,

Mark

Hi


  f.dims <- c(10,25,1,1,1,14)
  m.dims <- c(10, 1,1,1,1,14)
  f <- array(1:prod(f.dims),f.dims)
  m <- array(1:prod(m.dims),m.dims)
  jj <- do.call(abind,c(rep(list(m),25),along=2))


Then

f + jj

will give you what you want.


The more general problem is a bit harder, as you say....


HTH

rksh


On 27 Apr 2007, at 10:41, Mark Payne wrote:
> Gudday,
>
> I've had a good look everywhere trying to figure out how to do  
> this, but
> I'm afraid I can seem to find an answer anywhere - maybe its  
> because I'm
> not using the right terms, or maybe its because I'm a dummy. But
> unfortunately, I am not completely and utterly stuck. Here's the
> problem:
>
> I have two large, six dimensional arrays that I would like to add
> together. Lets call them f and m. Their dimensions are respectively:
>
>> dim(f)
> [1] 10  25  1  1  1 14
>> dim(m)
> [1] 10 1 1 1 1 14
>
> You can see that they're pretty close in size, but not identical.  
> What I
> would like to do is expand or inflate m along its second dimension so
> that it ends up with dimension 10 25 1 1 1 14, so that I can then add
> the two together - the new values created along that second dimension
> would simply be copies of the first value..
>
> What's the fastest way to do this? Is there a dedicated function?
> Ideally I envisage something that you feed the input array, and the
> desired dimensions, and it does the rest for you. Please also bear in
> mind that this is a specific problem - the more general case is  
> where I
> don't know which dimensions are "out of shape", so to
speak...
>
> I hope that's clear, and that someone can me out here...
>
> Cheers,
>
> Mark
>
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