[R] Antwort: Fw: Re: Subscripting problem with is.na()

[PIKAL Petr]

Hi

see in line

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
> G.Maubach at weinwolf.de
> Sent: Monday, June 27, 2016 10:45 AM
> To: David L Carlson <dcarlson at tamu.edu>; Bert Gunter
> <bgunter.4567 at gmail.com>
> Cc: r-help at r-project.org
> Subject: [R] Antwort: Fw: Re: Subscripting problem with is.na()
>
> Hi David,
> Hi Bert,
>
> many thanks for the valuable discussion on NA in R (please see extract
> below). I follow your arguments leaving NA as they are for most of the
> time. In special occasions however I want to replace the NA with another
> value. To preserve the newly acquired knowledge for me I wrote this
> function:
>
> -- cut --
> t_replace_na <- function(dataset, variable, value) {
>  if(inherits(dataset[[variable]], "factor") == TRUE) {
>    dataset[variable] <- as.character(dataset[variable])
>    print(class(dataset[variable]))
>    dataset[, variable][is.na(dataset[, variable])] <- value
>    dataset[variable] <- as.factor(dataset[variable])
>    print(class(dataset[variable]))
>  } else {
>    dataset[, variable][is.na(dataset[, variable])] <- value
>  }
>  return(dataset)
> }
>

<snip>

> class(ds_test[, "c"])
> test_class(ds_test, "c")
> warning("'c' should be factor NOT data.frame.
> In addition data.frame != factor")
> -- cut --
>
> Why do I get different results for the same function if it is inside or
> outside my own function definition?

Because you still are missing the way how to subscript data frames.

test_class <- function(dataset, variable) {
  if(inherits(dataset[, variable], "factor") == TRUE) {
    return(c(class(dataset[,variable]), TRUE))
####                                 ^^^^
} else {
    return(c(class(dataset[,variable]), FALSE))
######                            ^^^^
  }
}

> test_class(ds_test, "a")
[1] "numeric" "FALSE"
> test_class(ds_test, "c")
[1] "factor" "TRUE"
>

If you properly arrange commas in your function you get desired result

p_replace_na <- function(dataset, variable, value) {
 if(inherits(dataset[,variable], "factor") == TRUE) {
   dataset[,variable] <- as.character(dataset[,variable])
   print(class(dataset[,variable]))
   dataset[, variable][is.na(dataset[, variable])] <- value
   dataset[, variable] <- as.factor(dataset[, variable])
   print(class(dataset[, variable]))
 } else {
   dataset[, variable][is.na(dataset[, variable])] <- value
 }
 return(dataset)
}

> p_replace_na(ds_test, "c", value = -3)
[1] "character"
[1] "factor"
   a  b  c
1  1 NA  A
2 NA NA  b
3  2 NA -3

> t_replace_na(ds_test, "c", value = -3)
[1] "data.frame"
Error in sort.list(y) : 'x' must be atomic for 'sort.list'
Have you called 'sort' on a list?
>

Cheers
Petr



>
> Kind regards
>
> Georg
>
> --------------------------------
>
> > Gesendet: Donnerstag, 23. Juni 2016 um 21:14 Uhr
> > Von: "David L Carlson" <dcarlson at tamu.edu>
> > An: "Bert Gunter" <bgunter.4567 at gmail.com>
> > Cc: "R Help" <r-help at r-project.org>
> > Betreff: Re: [R] Subscripting problem with is.na()
> >
> > Good point. I did not think about factors. Also your example raises
> another issue since column c is logical, but gets silently converted to
> numeric. This would seem to get the job done assuming the conversion is
> intended for numeric columns only:
> >
> > > test <- data.frame(a=c(1,NA,2), b = c("A","b",NA), c= rep(NA,3))
> > > sapply(test, class)
> >         a         b         c
> > "numeric"  "factor" "logical"
> > > num <- sapply(test, is.numeric)
> > > test[, num][is.na(test[, num])] <- 0
> > > test
> >   a    b  c
> > 1 1    A NA
> > 2 0    b NA
> > 3 2 <NA> NA
> >
> > David C
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

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