[R] Replecing empty values with a letter (continuation)

[David Winsemius]

Judith Flores <juryef at yahoo.com> wrote in
news:32500.45083.qm at web34708.mail.mud.yahoo.com: 

> Sorry, I hit the send botton by accident. Here is my
> code so far:
> 
> dat<-read.csv('myfile.csv', na.strings="")
> dat[is.na(dat]<-'N'
> 
>    But it doesn't replace the <NA> for the letter 'N'.
> 
> 
What happens when you just type:

dat[is.na(dat)]   #?

My guess is that you don't have any, since na.strings="" told 
read.table that there were no values that should be assigned <NA>. It 
is possible to have a value of "NA" that is not <NA>.

> x <- c("NA", 1 , 2)
#NA is not <NA>
> is.na(x)
[1] FALSE FALSE FALSE
> txt <- "nnn 1 2 3 4 5"
> xt<- read.table(textConnection(txt), header=FALSE)
> xt
   V1 V2 V3 V4 V5 V6
1 nnn  1  2  3  4  5
> xt<- read.table(textConnection(txt), header=FALSE,na.strings="nnn")
> xt
  V1 V2 V3 V4 V5 V6
1 NA  1  2  3  4  5

#That is a TRUE >NA>
> is.na(xt)
       V1    V2    V3    V4    V5    V6
[1,] TRUE FALSE FALSE FALSE FALSE FALSE

> xt[is.na(xt)] <- "N"
> xt
  V1 V2 V3 V4 V5 V6
1  N  1  2  3  4  5


-- 
David Winsemius