[R] plyr package: passing further arguments fail

hadley wickham h.wickham at gmail.com
Sun Oct 5 15:39:16 CEST 2008

On Sun, Oct 5, 2008 at 8:02 AM, Auguie, Baptiste <ba208 at exeter.ac.uk> wrote:
> Dear list and Hadley,
> The new plyr package seems to provide a clean and consistent way to apply a function on several arguments. However, I don't understand why the following example does not work like the standard mapply,
> library(plyr)
> df <- data.frame(a=1:10 , b=1:10)
> foo1 <- function(a, b, cc=0, d=0){
>        a + b + cc + d
> }
> mdply(df, foo1, cc=1) # fine
> mdply(df, foo1, d=1) # fails
> mdply(df, foo1, cc=1, d=2) # fails

Unfortunately this bug is R's partial name matching: d = 2 -> data. =
2.  You should be able to fix this by manually specifying mdply(data.
= df, foo1, cc=1, d=2) but there are some bugs in the current version
that prevent this from happening.  I've fixed this in the development
version, available from http://github.com/hadley/plyr (click the
download link)

However, the whole point of plyr is that you should have to think
about this kind of thing, so I'll revisit my naming scheme - probably
to use . prefixes instead of suffixes.



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