[R] logistf error message

[Van Dyke, Alison]

I am new to using R.  Currently, I am using the logistf package to run logistic regression analysis.  When I run the following line of code:
 
attach(snpriskdata)
logisticpaper<-logistf(sascasecon~saspackyrs+newsbmi+EDUCATION+sasagedx+sasflung+condobst+sasadultasprev)
 
I get the following error message:
 
Error in sum(y) : invalid 'type' (character) of argument
 
What does this error message mean?  All of my variables are in numeric format.  Thank you for your input.
 
Alison Van Dyke
Wayne State University