[R] Subscripting problem with is.na()

[Ivan Calandra]

Dear Georg,

You need to learn a bit more about the subsetting methods, depending on 
the object structure you're trying to subset.

More specifically, when you run this: ds_test[is.na(ds_test$var1)]
you get this error: "Error in `[.data.frame`(ds_test, 
is.na(ds_test$var1)) : undefined columns selected"

This means that R does not understand which column you're trying to 
select. But you're actually trying to select rows.

Using a single bracket '[' on a data.frame does the same as for 
matrices: you need to specify rows and columns, like this:
ds_test[is.na(ds_test$var1), ] ## notice the last comma
ds_test[is.na(ds_test$var1), ] <- 0 ## works on all columns because you 
didn't specify any after the comma

If you want it only for "var1", then you need to specify the column:
ds_test[is.na(ds_test$var1), "var1"] <- 0

It's the same problem with your 2nd and 4th tries (4th one has other 
problems). Your 3rd try does not change ds_test at all.

HTH,
Ivan

--
Ivan Calandra, PhD
Scientific Mediator
University of Reims Champagne-Ardenne
GEGENAA - EA 3795
CREA - 2 esplanade Roland Garros
51100 Reims, France
+33(0)3 26 77 36 89
ivan.calandra at univ-reims.fr
--
https://www.researchgate.net/profile/Ivan_Calandra
https://publons.com/author/705639/

Le 23/06/2016 à 15:57, G.Maubach at weinwolf.de a écrit :
> Hi All,
>
> I would like to recode my NAs to 0. Using a single vector everything is
> fine.
>
> But if I use a data.frame things go wrong:
>
> -- cut --
>
> var1 <- c(1:3, NA, 5:7, NA, 9:10)
> var2 <- c(1:3, NA, 5:7, NA, 9:10)
> ds_test <-
>    data.frame(var1, var2)
>
> test <- var1
> test[is.na(test)] <- 0
> test  # NA recoded OK
>
> # First try
> ds_test[is.na(ds_test$var1)] <- 0  # duplicate subscripts WRONG
>
> # Second try
> ds_test[is.na("var1")] <- 0
> ds_test$var1  # not recoded WRONG
>
> # Third try: to me the most intuitive approach
> is.na(ds_test["var1"]) <- 0  # attempt to select less than one element in
> integerOneIndex WRONG
>
> # Fourth try
> ds_test[is.na(var1)] <- 0  # duplicate subscripts for columns WRONG
>
> -- cut --
>   
> How can I do it correctly?
>
> Where could I have found something about it?
>
> Kind regards
>
> Georg
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>