Hi,
Does anyone why the following code produces different results?
a <- cbind(1:10,1:10)
b <- a
colnames(a) <- c("a","b")
colnames(b) <- c("c","d")
colnames(cbind(a,b))
> [1] "a" "b" "c" "d"
colnames(cbind(ts(a),ts(b)))
> [1] "ts(a).a" "ts(a).b" "ts(b).c" "ts(b).d"
Is this or compatibility reasons? Cbind for xts and zoo does not have this
feature. I checked the code for stats:::.cbind.ts and the offending piece of
code is the following:
ns <- sum(nsers)
x <- matrix(, n, ns)
cs <- c(0, cumsum(nsers))
nm <- character(ns)
for (i in 1L:nser) if (nsers[i] > 1) {
cn <- colnames(sers[[i]])
if (is.null(cn))
cn <- 1L:nsers[i]
nm[(1 + cs[i]):cs[i + 1]] <- paste(nmsers[i], cn,
sep = ".")
}
else nm[cs[i + 1]] <- nmsers[i]
Where nsers is the output of .makeNamesTs and nm is the names of the final
cbinded object. There is quite an effort to make the names of cbinded ts object
different from the result of cbinded matrix, or data.frame where the resulting
name is simply concatenated vector of colnames of objects which are cbinded. I
am interested to know why is that? In my experience, there is always a good
reason for they way R behaves precisely it does, so in this case maybe I'm
missing something. For my current needs I'm using the following function:
cbts <- function(...) {
dots <- list(...)
cnames <- unlist(lapply(dots,function(l){
if(is.null(dim(l)))""
else colnames(l)
}))
out <- do.call("cbind",dots)
colnames(out) <- cnames
out
}
I need this behaviour because I routinely pass ts objects to dynlm, or operate
on ts objects based on their names, so anything that changes the original name
is an inconvenience I need to work around.
I've already asked this question on stackoverflow, but did not get answers I
needed:
http://stackoverflow.com/questions/18488816/why-cbind-for-ts-objects-behaves-different-from-cbind-for-matrices-and-data-fram
Vaidotas Zemlys
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