Recode Variable

[David Studer]

Hello everybody,

I know this is pretty basic stuff, but could anyone explain me how to
recode a single value of a variable
into a missing value?

I used to do it like this:

myData[myData$var1==5;"var1"]<-NA             # recode value "5" into "NA"

But the column "var1" already contains NAs, which
results in the following error message:

"missing values are not allowed in subscripted assignments of data frames"

Thank you very much for any advice!

David

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[Tal Galili]

Hi David,
You bring up a good question.  I am not sure what is the "right" way to
solve it.  But here is a simple solution I put together:

x = c(1:10,5)
y = x
x[c(2,3)] <- NA

# reproducing the problem:
y[x==5]

na2F <- function(x) {
    x2 <- x
    x2[is.na(x)] <- F
    x2
}
na2F(x==5)

# "solved"
y[na2F(x==5)]


I'd be happy to see other solutions to it.

With regards,
Tal



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On Thu, Apr 12, 2012 at 12:08 PM, David Studer <[hidden email]> wrote:

> Hello everybody,
>
> I know this is pretty basic stuff, but could anyone explain me how to
> recode a single value of a variable
> into a missing value?
>
> I used to do it like this:
>
> myData[myData$var1==5;"var1"]<-NA             # recode value "5" into "NA"
>
> But the column "var1" already contains NAs, which
> results in the following error message:
>
> "missing values are not allowed in subscripted assignments of data frames"
>
> Thank you very much for any advice!
>
> David
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] 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.
>

        [[alternative HTML version deleted]]

______________________________________________
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[Milan Bouchet-Valat]

Le jeudi 12 avril 2012 à 12:29 +0300, Tal Galili a écrit :

> Hi David,
> You bring up a good question.  I am not sure what is the "right" way to
> solve it.  But here is a simple solution I put together:
>
> x = c(1:10,5)
> y = x
> x[c(2,3)] <- NA
>
> # reproducing the problem:
> y[x==5]
>
> na2F <- function(x) {
>     x2 <- x
>     x2[is.na(x)] <- F
>     x2
> }
> na2F(x==5)
>
> # "solved"
> y[na2F(x==5)]
>
>
> I'd be happy to see other solutions to it.

You can simply use the built-in function which() for this, since it
removes NAs, only returning the position of TRUE elements:
which(c(NA, 1:10 == 5))
[1] 6


My two cents

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[Milan Bouchet-Valat]

Le jeudi 12 avril 2012 à 11:08 +0200, David Studer a écrit :

> Hello everybody,
>
> I know this is pretty basic stuff, but could anyone explain me how to
> recode a single value of a variable
> into a missing value?
>
> I used to do it like this:
>
> myData[myData$var1==5;"var1"]<-NA             # recode value "5" into "NA"
>
> But the column "var1" already contains NAs, which
> results in the following error message:
>
> "missing values are not allowed in subscripted assignments of data frames"
>
> Thank you very much for any advice!

You can just do this:
myData <- data.frame(var1=1:10)
myData$var1[2]<-NA
myData[myData$var1 == 5, "var1"] <- NA # Fails
myData$var1[myData$var1 == 5] <- NA # Works
myData
   var1
1     1
2    NA
3     3
4     4
5    NA
6     6
7     7
8     8
9     9
10   10


Regards

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[Rainer Schuermann]

1. Some data structured the way you are using would have been helpful.
I used Tal Galil's play data and set up a dataframe with the variable names you are using:
structure(list(var1 = c(1, NA, NA, 4, 5, 6, 7, 8, 9, 10, 5),
    var2 = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 5)), .Names = c("var1",
"var2"), row.names = c(NA, -11L), class = "data.frame")
> myData
   var1 var2
1     1    1
2    NA    2
3    NA    3
4     4    4
5     5    5
6     6    6
7     7    7
8     8    8
9     9    9
10   10   10
11    5    5

2. The error message I get from your line of code is
> myData[myData$var1==5;"var1"]<-NA
Error: unexpected ';' in "myData[myData$var1==5;"
Probably the semikolon is a typo?

3. If I understand your question correctly, the easiest answer I can find is ifelse():
> myData$var1 <- ifelse( myData$var1 == 5, NA, myData$var1 )
> myData
   var1 var2
1     1    1
2    NA    2
3    NA    3
4     4    4
5    NA    5
6     6    6
7     7    7
8     8    8
9     9    9
10   10   10
11   NA    5

Rgds,
Rainer


On Thursday 12 April 2012 11:08:45 David Studer wrote:

> Hello everybody,
>
> I know this is pretty basic stuff, but could anyone explain me how to
> recode a single value of a variable
> into a missing value?
>
> I used to do it like this:
>
> myData[myData$var1==5;"var1"]<-NA             # recode value "5" into "NA"
>
> But the column "var1" already contains NAs, which
> results in the following error message:
>
> "missing values are not allowed in subscripted assignments of data frames"
>
> Thank you very much for any advice!
>
> David
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] 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.

______________________________________________
[hidden email] 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.

[S Ellison-2]

> myData[myData$var1==5;"var1"]<-NA             # recode value "5" into "NA"
try
myData[!is.na(myData$var1) & myData$var1==5;"var1"]<-NA
or, more simply,
myData$var1[myData$var1==5]<-NA

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