Among other uses of sapply(), I use to use it for
"analyzing" / "summarizing" components of a list or to
`summarize' objects
in my search path,
typically such as
sapply(obj.names, function(n){ r <- get(n);
unlist(r[c("x","y","par")]) })
which gives a list or a 3-col matrix (depending if "x",
"y","par" have always
same length..) that has no (row)names unfortunately, even though it's clear
that I would want my initial names...
for(n in 1:3)
assign(paste("o",n,sep=""), list(x=n,y=n^2,par=n/4))
(obj.n <- paste("o",1:3,sep=""))
sapply(obj.n, function(n){
unlist(get(n)[c("x","y","par")]) })
which gives
[,1] [,2] [,3]
x 1.00 2.0 3.00
y 1.00 4.0 9.00
par 0.25 0.5 0.75
but I would want
o1 o2 o3
x 1.00 2.0 3.00
y 1.00 4.0 9.00
par 0.25 0.5 0.75
----
I can get this with the following patch :
--- sapply.R 1999/01/29 17:39:28 1.3
+++ sapply.R 1999/09/24 16:12:53
@@ -1,8 +1,10 @@
-sapply <- function(X, FUN, ..., simplify = TRUE)
+sapply <- function(X, FUN, ..., simplify = TRUE, do.names = TRUE)
{
FUN <- match.fun(FUN)
-
answer <- lapply(as.list(X), FUN, ...)
+ if(do.names && is.null(names(answer))) { # create names if sensible
+ if(is.character(X)) names(answer) <- X
+ }
if(simplify && length(answer) &&
length(common.len <- unique(unlist(lapply(answer, length)))) == 1) {
if(common.len == 1)
---------------
Now, before implementing this:
1) is "do.names" proper naming or should we rather use
"DO.NAMES", "USE.NAMES", ...
(at the moment, I'd prefer USE.NAMES)
2) Inside the new if(do.names ....) { .... } clause,
we can try harder, e.g.,
if(do.names && is.null(names(answer))) { # create names if sensible
names(answer) <-
if(is.character(X)) X else abbreviate(deparse(substitute(X)))
}
- actually this wouldn't always work as desired;
`substitute(X)' would have to be saved
before the first use of X ( evaluation of expressions...)
- In that case, do.names (or USE.NAMES) should probably have
the default is.character(X) -- for efficiency & back-compatibility
Opinions?
Martin Maechler <maechler@stat.math.ethz.ch>
http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum LEO D10 Leonhardstr. 27
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
phone: x-41-1-632-3408 fax: ...-1228 <><
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