[R] Antwort: RE: Antwort: Fw: Re: Subscripting problem with is.na()
G.Maubach at weinwolf.de
G.Maubach at weinwolf.de
Mon Jun 27 13:43:13 CEST 2016
Hi Petr,
many thanks for your reply and the examples.
My subscripting problems drive me nuts.
I have understood that dataset[variable] is semantically identical to
dataset[, variable] cause dataset[variable] takes all cases because no
other subscripts are given.
Where can I lookup the rules when to use the comma and when not?
Kind regards
Georg
Von: PIKAL Petr <petr.pikal at precheza.cz>
An: "G.Maubach at weinwolf.de" <G.Maubach at weinwolf.de>,
Kopie: "r-help at r-project.org" <r-help at r-project.org>
Datum: 27.06.2016 11:03
Betreff: RE: [R] Antwort: Fw: Re: Subscripting problem with
is.na()
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
>
> ______________________________________________
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