R column assignment fails for lists

Dear Jim and David,

Thank you very much for your reply. I guess my question is whether it is
legal to store vectors in the elements of a data.frame. These are useful
for storing things like neighbors of a graph vertex, orthologs of a gene
etc. I have been using data frames of this sort and they are very useful,
so I am hoping this is a feature, rather than a bug. The weird code in my
email to form a was just one quick way of making such an object for a toy
example. These sort of data frames were doing fine for a number of analysis
pipelines until I used a function on them that had code of the sort
df[, j] <- sapply(df[, j], fun)

The interesting thing is that while
a[,3] <- a[,3] changes the object and gives the warning
a$c <- a$c works "correctly". leaving a to what it was and doesn't give a
warning.

If elements of a data frame are supposed to be able to store vectors, then
shouldn't
a[,3] <- a[,3] work?

Best regards,
yasir


On Tue, May 3, 2016 at 9:48 PM, David Winsemius <dwinsemius at comcast.net>
wrote:

On May 3, 2016, at 4:13 PM, Yasir Suhail <yasir.suhail at gmail.com> wrote:

Dear R developers and users,

Consider the object :

a <- data.frame(a=c(1,2), b=c(2,3), c=c("a,b","c,d"), stringsAsFactors

= F)

a$c <- strsplit(a$c, ",")

You are the one who should "consider the object". Look at what
strsplit(a$c, ",") returns and then perhaps re-consider trying to assign it
to a single column.

Re-assignment works fine for columns 1 and 2, but fails for column 3. If

a

is a valid object, the assignment should work.

a[,1] <- a[,1]
a[,2] <- a[,2]
a[,3] <- a[,3]

Warning message:
In `[<-.data.frame`(`*tmp*`, , 3, value = list(c("a", "b"), c("c",  :
 provided 2 variables to replace 1 variables

      [[alternative HTML version deleted]]

And please reconsider also the format of your postings.

______________________________________________
R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide

http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

David Winsemius
Alameda, CA, USA