This puzzle started with an SO posting where the questioner showed output from
a dataframe that had been indexed with a matrix. The output appeared to show
that numeric values had been coerced to character. Once I got a reproducible
example I discovered that the print output was the problem and that the actual
values had not been coerced. I've created a much smaller test case and it
appears from the testing below that a matrix indexed output from a dataframe
with mixed numeric and character types will be printed as character even if
none of the values indexed are character:
> dat <- setNames( as.data.frame( matrix(1:12, ncol=4) ), LETTERS[1:4])
> dat
A B C D
1 1 4 7 10
2 2 5 8 11
3 3 6 9 12
> dat[2,4]<-NA
> dat[3,3]<-NA
> ng <- which(is.na(dat), arr.ind=TRUE)
> ng
row col
[1,] 3 3
[2,] 2 4
> dat[ng] <- 20
> dat[ng]
[1] 20 20
That was as expected. Now repeat the process with a dataframe of mixed types.
> dat[2,4]<-NA
> dat[3,3]<-NA
> dat[,1]<- "a"
> dat
A B C D
1 a 4 7 10
2 a 5 8 NA
3 a 6 NA 12
> dat[ng] <- 20
> dat[ng]
[1] "20" "20"
Quoted print output was not what I was expecting.
--
David Winsemius
Alameda, CA, USA
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