R help - May 2004 - Change in how R handles assignments?

Dear R-users and experts,

I have been using the following code in earlier versions of R:

  q[,names(info)]<-info[no,];

with
> class(info)
[1] "data.frame"
> class(q)
[1] "data.frame"
> dim(q)
[1] 7488   68
> dim(info)
[1] 12  8
> dim(info[no,])
[1] 1 8

The column names(info) did not exist in q before the assignment.

What used to happen (as intended) was that they would be created, and each of 
the 7488 rows would be set the same value, info[no,].

Now, in the current version of R this gives the error:

Error in "[[<-.data.frame"(`*tmp*`, k, value = rep(value[[k]], len
= n)) :
	replacement has 7488 rows, data has 1

I can use the following as a workaround

    for (n in names(info))
      q[,n]<-info[no,n];

but it seems clunky. Is there a more elegant/simple way to do the same thing 
in the current version of R? It seems I'm unintentionally forcing it to do 
something it doesn't "like".

Comments much appreciated.

Best regards,

David.


------------------------------------------------------------------------
Dr David Philip Kreil                
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Research Fellow                        `6_ 6  )   `-.  (     ).`-.__.`)
University of Cambridge                (_Y_.)'  ._   )  `._ `. ``-..-'
++44 1223 764107, fax 333992         _..`--'_..-_/  /--'_.' ,'
www.inference.phy.cam.ac.uk/dpk20   (il),-''  (li),'  ((!.-'

Note, this is how R handles `replacement subsetting of data frames'.

On Mon, 17 May 2004, David Kreil wrote:
> I have been using the following code in earlier versions of R:
What `earlier versions'?  As far as I know this was changed in 1.8.0.
>   q[,names(info)]<-info[no,];
You do not need to terminate lines in ;, BTW.
> with
> 
> > class(info)
> [1] "data.frame"
> > class(q)
> [1] "data.frame"
> > dim(q)
> [1] 7488   68
> > dim(info)
> [1] 12  8
> > dim(info[no,])
> [1] 1 8
> 
> The column names(info) did not exist in q before the assignment.
> 
> What used to happen (as intended) was that they would be created, and each
of
> the 7488 rows would be set the same value, info[no,].
But that was not what was documented.  The intention is that the rhs be a 
list, not a data frame.
> Now, in the current version of R this gives the error:
> 
> Error in "[[<-.data.frame"(`*tmp*`, k, value = rep(value[[k]],
len = n)) :
> 	replacement has 7488 rows, data has 1
> 
> I can use the following as a workaround
> 
>     for (n in names(info))
>       q[,n]<-info[no,n];
> 
> but it seems clunky. Is there a more elegant/simple way to do the same
thing
> in the current version of R? It seems I'm unintentionally forcing it to
do
> something it doesn't "like".
Here's a simple example that does the same in 1.8.0 as R-patched:

x <- data.frame(a=1:3, b=4:6, c=7:9)
info <- x[1:2]
x[, names(info)] <-  info[1, ]

You can do
x[, names(info)] <-  info[rep(1,3), ]
or
x[, names(info)] <- unclass(info[1, ])

We'll unclass a data frame rhs internally in future.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595