[R] Dataframes and assign

[Douglas Bates]

Göran Broström <gb at stat.umu.se> writes:

> I have the following function:
> 
> putsoc <- function(age, dat){
>   ## age is an integer
>   ## dat is a data.frame
> 
>   new.name <- paste("soc", as.character(age), sep = ".")
>   if (new.name %in% names(dat)) stop(paste(new.name, "already in place"))
> 
>   dat$new.var <- rep(1, nrow(dat)) ## Just nonsense.
> 
>   n.var <- ncol(dat)
>   names(dat)[ncol(dat)] <- new.name
>   return(dat)
> }

The $ operator is 'syntactic sugar' that allows you to write
frm$colname instead of frm[['colname']].  In your case you are
generating the name as a character string so you should use the second
form.  That is, write your function as

putsoc <- function(age, dat) {
   new.name <- paste("soc", as.character(age), sep = ".")
   if (new.name %in% names(dat)) stop(paste(new.name, "already in place"))
 
   dat[[new.var]] <- rep(1, nrow(dat))
   return(dat)
}

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