> -----Original Message-----
> From: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] On Behalf Of hadley wickham
> Sent: Wednesday, November 11, 2009 3:03 PM
> To: Peng Yu
> Cc: r-h...@stat.math.ethz.ch
> Subject: Re: [R] Is there a way to specify drop=FALSE as the
> global default?
>
> > See the above example. Is there a way to make 'drop=FALSE' as global
> > default, so that when I say 'tmp[,1]', R will treat it as
> > 'tmp[,1,drop=FALSE]'?
>
> The following code won't change the defaults, but it would at least
> let you know when you're making the mistake:
Or you could write wrapper functions for [ and [<- that
add the drop=FALSE argument. E.g.,
SS <- function(x, ..., drop=FALSE) x[..., drop=drop] # 'Safe
Subscripting'
`SS<-` <- function(x, ..., value) { x[...] <- value ; x }
Use them as
SS(x, 1, i) # instead of x[1, i]
Use grep (or codetools::walkCode) to make sure you don't
have any other calls to [ in your code. (The ss<- is
there only so calls to [ on the left side of the assignment
don't attract grep's attention.)
S+ has a subscript2d() that does this and also lets
you use 2 subscripts on vectors (the 2nd must be 1
in that case, but you don't need to use if statements).
subscript2d doesn't even have the drop= argument - if
you want to make a vector from a one column matrix use
as.vector.
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
>
> trace_all <- function(fs, tracer) {
> lapply(fs, trace, exit = tracer, print=FALSE)
> invisible()
> }
>
> functions_with_arg <- function(arg, pos) {
> fs <- ls(pos=pos)
> present <- unlist(lapply(fs, function(x)
> is.function(get(x)) && !is.null(formals(x)[[arg]])))
>
> fs[present]
> }
>
> trace_all(
> functions_with_arg("drop", "package:base"),
> quote(if (drop) warning("drop = TRUE", call. = F))
> )
>
> > mtcars[1, 2]
> [1] 6
> Warning message:
> drop = TRUE
>
> Unfortunately it doesn't pick up on the generic [ because it
> is a primitive.
>
> Hadley
>
>
> --
> http://had.co.nz/
>
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>
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