R help - Oct 2009 - rbind to array members‏

(resent as hotmail really cannot format plaintext, but I've just read
Tony Plate's message that what I'd like to do might not be
possible)
>
> library(abind)  ## array binding
I've looked into using abind() but it seems I might not understand it
properly.

I can build my 2 table array and insert a row into each table using:

        x <- array(0,c(1,3,2))

        x[,,1] <- c(1,2,3)

        x[,,2] <- c(7,8,8)


And I can use rbind() or abind() to add a row to the first table and
assign it to a separate object.

        y <- rbind(x[,,1], c(4,5,6))
or
        z <- abind(x[,,1], c(4,5,6),along=0)


But I can't determine how to add a row in place to a single table of
the 3-dimensional array. For example, this does not work:

        x[,,1] <- abind(x[,,1], c(4,5,6),along=0)
            Error in x[, , 1] <- abind(x[, , 1], c(4, 5, 6), along = 0) :
              number of items to replace is not a multiple of replacement length

Using the above code, I would somehow like 'x' to be:
> x
, , 1

     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6

, , 2

     [,1] [,2] [,3]
[1,]    7    8    9


Thanks for any help.

	[[alternative HTML version deleted]]

> ? ? ? ?z <- abind(x[,,1], c(4,5,6),along=0)
z is probably not what you want because you aren't using the drop=FALSE
argument.  See the FAQ 7.5


abind, and arrays in general, are rectangular solids.  They are not
ragged.  For that you need lists.  To get something like your
request
> x
> , , 1
>
> ? ? [,1] [,2] [,3]
> [1,] ? ?1 ? ?2 ? ?3
> [2,] ? ?4 ? ?5 ? ?6
>
> , , 2
>
> ? ? [,1] [,2] [,3]
> [1,] ? ?7 ? ?8 ? ?9
>
you need
> x <- list(matrix(1:6, 2, 3, byrow=TRUE),
+           matrix(7:9, 1, 3))
> x
[[1]]
     [,1] [,2] [,3]
[1,]    1    2    3
[2,]    4    5    6

[[2]]
     [,1] [,2] [,3]
[1,]    7    8    9
>