[R] factor variables in logistic regression

[chalabi.elahe at yahoo.de]

Hi all,

I have a plot for TSTMean vs. SNRMean and both of these variables are factors. How can I use Logistic Regression for factor variables?
Currently I use model=lm(TSTMean~SNRMean,data=df) but when I check summary(model) I get this error: r error in quartile.default (resid) factors are not allowed
 
thanks for any help,
Elahe