[R] Error in contrasts message when using logistic regression code.
marc_schwartz at me.com
Tue Oct 23 21:40:14 CEST 2012
On Oct 23, 2012, at 1:43 PM, hoguejm <hoguejm at gmail.com> wrote:
> I have a rather large data set (about 30 predictor variables)
> I need to preform a logistic regression on this data. My response variable
> is binary.
> My code looks like this:
> mylogit <- glm(Enrolled ~ A + B + C + ... + EE, data = data, family =
> with A,B,C, ... as my predictor variables. Some categorical, some
> continuous, some binary.
> I run the code and get this error:
> Error in `contrasts<-`(`*tmp*`, value = contr.funs[1 + isOF[nn]]) :
> contrasts can be applied only to factors with 2 or more levels
> Any ideas on how to fix this? I am fairly new to R so Im guessing there is
> something missing/wrong in my logit code.
More than likely, one or more of your categorical variables are not set up as factors, or if they are, then one or more have only a single factor level present in the dataset that is used for the model, thus are constant.
You might want to run:
# see ?str
# see ?summary
to get a sense of the structure of your data set (to make sure that you have factors and not character vectors) and to get a sense for the distribution of your IVs.
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