[R] assigning to data frames with whole columns of NAs

[Uwe Ligges]

David Firth wrote:
> 
> I suppose this could be described as a feature (it seems to be similar in S-Plus), but it looks to me more like a bug.  Why can't the assignment below to a row of "emptyframe" (or "anotherframe") be made?  This with R --vanilla (version info below).

> 
> > emptyframe<-data.frame(a=c(NA,NA),b=c(NA,NA))
> > emptyframe
>    a  b
> 1 NA NA
> 2 NA NA
> > emptyframe[1,]<-c(1,2)
> Warning messages:
> 1: invalid factor level, NAs generated in: [<-.factor(*tmp*, iseq, value = vjj)
> 2: invalid factor level, NAs generated in: [<-.factor(*tmp*, iseq, value = vjj)

OK. That's not a bug! 
str(emptyframe) tells us: $a and $b are factors. You cannot assign the
*levels* "1" or "2" on this way.
So we can generate another similar example:
  emptyframe <- data.frame(a=c("A", "B"), b=c("A", "B"))
  str(emptyframe)
  emptyframe[1,] <- c(1, 2) # Don't work either, what we expect.


> > emptyframe
>    a  b
> 1 NA NA
> 2 NA NA
> > anotherframe<-data.frame(a=c(8,9),b=c(NA,NA))
> > anotherframe
>   a  b
> 1 8 NA
> 2 9 NA
> > anotherframe[1,]<-c(1,2)
> Warning message:
> invalid factor level, NAs generated in: [<-.factor(*tmp*, iseq, value = vjj)
> > anotherframe
>   a  b
> 1 1 NA
> 2 9 NA
> > yetanotherframe<-data.frame(a=c(8,NA),b=c(9,NA))
> > yetanotherframe
>    a  b
> 1  8  9
> 2 NA NA
> > yetanotherframe[1,]<-c(1,2)   #  no problem with this one
> > yetanotherframe
>    a  b
> 1  1  2
> 2 NA NA

Right, because here $a and $b are numeric: str(yetanotherframe)

If you really want to generate a data.frame only with NAs in it, you can
use for example:
  emptyframe <- data.frame(a=as.numeric(c(NA, NA)), b=as.numeric(c(NA,
NA)))
  emptyframe[1,] <- c(1, 2) # Works now ...

 
Uwe Ligges
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