[R] Recoding variables in R

[William Dunlap]

It looks like your data has class "factor".  If you call factor() on a
factor variable, without supplying an explicit 'levels' argument it
produces a new factor variable without any levels not present in the input
factor.  E.g.,

> fOrig <- factor(c(NA,"A","B","D",NA,"D"), levels=c("D","C","B","A"))
> summary(fOrig)
   D    C    B    A NA's
   2    0    1    1    2
> fNew <- factor(fOrig)
> summary(fNew)
   D    B    A NA's
   2    1    1    2

You can use levels(fNew) <- c("delta","beta","alpha") to give the levels
new names.

I think that renaming "0", "2", "3"  to "0","1","2" will lead to
confusion.  The levels
are just names, so give them names that mean something to a human, like
"control",
"streptomycin (2 mg/kg)", etc.


Bill Dunlap
TIBCO Software
wdunlap tibco.com

On Wed, May 23, 2018 at 3:14 AM, Lisa van der Burgh <lisavdburgh using hotmail.com
> wrote:

> Hi all,
>
>
> I have a very general question and I think for you maybe very easy, but I
> am not able to solve it.
>
> I have a dataset and that dataset contains the variable Anxiolytics. This
> variable is coded as 0, 1, 2. The variable looks as follows:
>
>
> > summary(DF$Anxiolytics)
>    0        1     2       NA's
> 1102   0     20    440
>
>
> You can see that the variable is coded as 0, 1, 2, but group 1 is 'empty'.
> So I want to remove this group, such that I get:
>
> > summary(DF$Anxiolytics)
>    0          2       NA's
> 1102     20      440
>
> And then I want to recode the variable in a way that 2 becomes 1, such as:
>
> > summary(DF$Anxiolytics)
>    0          1       NA's
> 1102     20      440
>
> Can you help me with the code for doing this?
>
> Thank you in advance!
> Best, Lisa
>
>
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>
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