[R] "missings=function(x) x[x==998|x==999]<-NA" doesn't work...

[Ben Tupper]

Hi,

On Sep 18, 2014, at 10:13 AM, Doreen Mueller <Doreen.Mueller at dza.de> wrote:

> Hi!
> 
> I want to have a function that assigns NAs to certain values of my 
> variable "var" in the dataset "d". This doesn't work:
> 
>> missings=function(x) x[x==998|x==999]<-NA
>> missings(d$var)
>> table(d$var, useNA="always")
> 
>    0      1  999 <NA> 
> 220  752  321 5264 
> 
> I don't get any error messages, but "d$var" remains unchanged. The 
> function:
>> missings=function(x) x[x==90|x==99]<<-NA
> doesn't work either, and I read that "<<-" is "dangerous" anyway?
> 

You are so close.  R returns the value of the last thing evaluated in your function.  In this case, the *copy* of your input argument was modified within the function, but you didn't return the value of the copy to the calling environment.  You need to explicitly return the modified value.

> missings <- function(x) { x[ (x==998) | (x==999) ] <- NA ; return(x) }
> missings(990:1010)
 [1]  990  991  992  993  994  995  996  997   NA   NA 1000 1001 1002 1003 1004 1005 1006 1007
[19] 1008 1009 1010

By the way, don't forget to switch your email client to use text instead of html when sending a message to the list.

Cheers,
Ben





> It is important for me to work with variable names (and therefore with 
> functions instead loops) because the number and order of variables in my 
> dataset changes regularly.
> 
> Thank you,
> Doreen
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.