[R] Help with creating conditional categorical variables in R

R. Michael Weylandt michael.weylandt at gmail.com
Wed Apr 18 17:35:38 CEST 2012

Your problem is that columns A & B contain something that can't be
ordered. (Likely "factor" (=categorical) data like Male / Female
rather than numeric like 10 and 5)

Use str(data_2) to see what classes your data are -- they sometimes
get converted in unexpected ways if you aren't careful in setting up
your data.frame. If this doesn't clear things up, please type
dput(head(data_2, 20)) at the console and copy and paste the result
into a follow up email.

Don't do the data.matrix thing without understanding the current class
of your data -- you'll get strange conversions.

Hope this helps,

On Wed, Apr 18, 2012 at 8:36 AM, Dwaipayan Dasgupta
<Dwaipayan.Dasgupta at aexp.com> wrote:
> Hi,
> I am stuck with creating a conditional categorical variable in R
> If my dataframe  data_2  has 3 variables A,B,C    I want to create variable D which would be something like :
> data_2$D <- ifelse(data_2$A < data_2$B & promotion_ind =="N",1,0),
> this throws up an error "In Ops.factor(data_2$A,data_2$B) :
>  < not meaningful for factors
> I have tried converting the dataframe to a matrix using
> data.matrix(data_2, rownames.force = NA) but that did not help,
> Can anybody tell me how to go about doing this?
> Thanks in advance,
> Doy
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