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

[Peter Dalgaard BSA]

David Firth <david.firth at nuffield.oxford.ac.uk> writes:

> > 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) 

Problem, what problem?

> emptyframe  
   a  b
1 NA NA
2 NA NA
> emptyframe[1,]<-c(1,2)
> emptyframe
   a  b
1  1  2
2 NA NA

OK, I'm pulling your leg. The snag is that NA is logical NA, unless
something coerces it to something else, and when constructing data
frames, logical vectors are coerced to factors. So I had defined:

> emptyframe<-data.frame(a=as.numeric(c(NA,NA)),b=as.numeric(c(NA,NA)))

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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