R help - May 2013 - Could graph objects be stored in a "two-dimensional list"?

Hi,

  I have a few graph objects created by some graphic package (say, ggplot2,
which I use frequently). Because of the existent relation between the
graphs, I'd like to index them in two dimensions as p[1,1], p[1,2], p[2,1],
p[2,2] for convenience.

  To my knowledge, the only data type capable of storing graph objects (and
any R object) is list, but unfortunately it is available in only one
dimension. Could the graphs be stored in any two-dimensional data type?

  One remedy that comes to my mind is to build a function f so that
f(1,1)=1
f(1,2)=2
f(2,1)=3
f(2,2)=4
  With functions f and f^{-1} (inverse function of f) , the two-dimensional
indices could be mapped to and from a set of one-dimensional indices, and
the functions are exactly the way R numbers elements in a matrix. Does R
have this built-in function for a m by n matrix or more generally, m*n*p
array? (I know this function is easy to write, but just want to make sure
whether it exists already)

   Thanks,

Miao

	[[alternative HTML version deleted]]

You could use lists of lists, and index them with vectors.

a <- list()
a[[1]] <- list()
a[[2]] <- list()
a[[c(1,1)]] <- g11
a[[c(1,2)]] <- g12
a[[c(2,1)]] <- g21
a[[c(2,2)]] <- g22
print(a[[c(2,1)]])

but this seems like an inefficient use of memory because your indexed data is
stored more compactly than the graph object is. I would index the data and
generate the graph object on the fly when I wanted to see it.
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jpm miao <miaojpm at gmail.com> wrote:
>Hi,
>
>I have a few graph objects created by some graphic package (say,
>ggplot2,
>which I use frequently). Because of the existent relation between the
>graphs, I'd like to index them in two dimensions as p[1,1], p[1,2],
>p[2,1],
>p[2,2] for convenience.
>
>To my knowledge, the only data type capable of storing graph objects
>(and
>any R object) is list, but unfortunately it is available in only one
>dimension. Could the graphs be stored in any two-dimensional data type?
>
>  One remedy that comes to my mind is to build a function f so that
>f(1,1)=1
>f(1,2)=2
>f(2,1)=3
>f(2,2)=4
>With functions f and f^{-1} (inverse function of f) , the
>two-dimensional
>indices could be mapped to and from a set of one-dimensional indices,
>and
>the functions are exactly the way R numbers elements in a matrix. Does
>R
>have this built-in function for a m by n matrix or more generally,
>m*n*p
>array? (I know this function is easy to write, but just want to make
>sure
>whether it exists already)
>
>   Thanks,
>
>Miao
>
>	[[alternative HTML version deleted]]
>
>______________________________________________
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>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.

On May 23, 2013, at 8:30 AM, jpm miao wrote:
> Hi,
> 
>  I have a few graph objects created by some graphic package (say, ggplot2,
> which I use frequently). Because of the existent relation between the
> graphs, I'd like to index them in two dimensions as p[1,1], p[1,2],
p[2,1],
> p[2,2] for convenience.
> 
>  To my knowledge, the only data type capable of storing graph objects
(This will all be depending on what you do mean by "graph objects".)
> (and
> any R object) is list, but unfortunately it is available in only one
> dimension.
I think both of these presumptions are incorrect.
> Could the graphs be stored in any two-dimensional data type?
> 
>  One remedy that comes to my mind is to build a function f so that
> f(1,1)=1
> f(1,2)=2
> f(2,1)=3
> f(2,2)=4
>  With functions f and f^{-1} (inverse function of f) , the two-dimensional
> indices could be mapped to and from a set of one-dimensional indices, and
> the functions are exactly the way R numbers elements in a matrix. Does R
> have this built-in function for a m by n matrix or more generally, m*n*p
> array? (I know this function is easy to write, but just want to make sure
> whether it exists already)
> 
Matrices can hold list elements:
> matrix( list(a="a"), 2,2)
     [,1] [,2]
[1,] "a"  "a" 
[2,] "a"  "a" 
> matrix( list(a="a"), 2,2)[1,1]
[[1]]
[1] "a"


And list may be nested in a regular "matrix"
> list( list( list(a="a"), list(b="bb") ), 
       list(list(c="ccc"), list(d="dddd") ) )[[1]][[2]]
$b
[1] "bb"


So storing in this manner for access by an appropriately designed function
should also be straight-forward. You could argue that the lattice-object panel
structure depends on this fact.
> 
> 	[[alternative HTML version deleted]]
Please learn to post  in plain text.

David Winsemius
Alameda, CA, USA