[R] conditional selection with Factors

From: H J Gerber <Gerbehj_at_unisa.ac.za>
Date: Wed 06 Apr 2005 - 19:34:07 EST

Hi All,  

I want to select a level of a factor variable from a dataset. I have the folowing data: dataset: use
factor: month (use$month, levels=February, July)
> use[1:5,]

     month registration use  department size
1 February     KKG151GP   Y      Safety  1.6
To select February I tried:
> use[use$month=="February"]

Error in "[.data.frame"(use, use$month == "February") :

        undefined columns selected
> use[use$month == levels(use$month)[1]]
Error in "[.data.frame"(use, use$month == levels(use$month)[1]) :

        undefined columns selected
It seems if a logical variable is created, and the subsetting on a factor variable won't work directly.(It works directly for numeric variables) Can anyone help please.  

Hennie Gerber  

Hennie Gerber
UNISA - Research Support
+ 27 12 429 3188
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