R help - Apr 2008 - Replecing empty values with a letter (continuation)

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'.


     I am using R v 2/7/0, running it under Windows
XP.

Thank you,

Judith


     
____________________________________________________________________________________
Be a better friend, newshound, and

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

Judith

I think you'll find the issue is that read.csv creates a data.frame and
your subsetting syntax
dat[is.na(dat)] is assuming it to be a matrix.  If this is the case, you
have two options:

Coerce dat into a matrix with as.matrix(dat);
Use apply() to replace the missing data for each column in turn ...
apply(dat, 2, function(x) x[is.na(x)] <- 'N')

HTH .......

Peter Alspach

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Judith Flores
> Sent: Thursday, 24 April 2008 11:20 a.m.
> To: RHelp
> Subject: [R] Replecing empty values with a letter (continuation)
> 
> 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'.
> 
> 
>      I am using R v 2/7/0, running it under Windows XP.
> 
> Thank you,
> 
> Judith
> 
> 
>       
> ______________________________________________________________
> ______________________
> Be a better friend, newshound, and
> 
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> R-help at r-project.org mailing list
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