[R] merging

[Gavin Simpson]

On Tue, 2006-05-30 at 15:09 -0500, Sundar Dorai-Raj wrote:
> 
> Gavin Simpson wrote:
> > Dear List,
<snip />
> 
> Will this help:
> 
> rbind.all <- function(...) {
>    x <- list(...)
>    cn <- unique(unlist(lapply(x, colnames)))
>    for(i in seq(along = x)) {
>      if(any(m <- !cn %in% colnames(x[[i]]))) {
>        na <- matrix(NA, nrow(x[[i]]), sum(m))
>        dimnames(na) <- list(rownames(x[[i]]), cn[m])
>        x[[i]] <- cbind(x[[i]], na)
>      }
>    }
>    do.call(rbind, x)
> }
> 
> y <- matrix(c(0,1,1,1,0,0,0,4,4), ncol = 3, byrow = TRUE)
> rownames(y) <- c("a","b","c")
> colnames(y) <- c("1","2","3")
> y2 <- y[2:3, 2:3]
> rownames(y2) <- c("x","z")
> y3 <- matrix(c(0,1,1,1,0,0,0,4,4,5,6,7), ncol = 4, byrow = TRUE)
> rownames(y3) <- c("d","e","f")
> colnames(y3) <- c("1","2","3","4")
> 
> rbind.all(y, y2, as.data.frame(y3))
> 
> It does very little error-checking, so be careful how you use it.
> 
> --sundar

Dear Marc and Sundar,

Thank you both for your solutions to my merging problem. Both work well
on the size of the real data sets this will be used on. In the end I
opted for Sundar's rbind.all() as it has the, welcome but unexpected,
side-effect of allowing you to merge more than 2 data frames at the same
time - which was something I was wanting to implement at a later date.

Sundar, I was thrown a little by the need to as.data.frame one of the
incoming matrices. If you leave it out you get very different results, I
assume because the matrix "method" is being used instead of
rbind.data.frame. It took me a little while to track this down as rbind
doesn't do method dispatch in the standard UseMethod way.

Once again, many thanks,

G

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Gavin Simpson
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