st: Collapse error: "Factor variables not allowed"

[Lynne Morgan <lmorgan3@wisc.edu>]

Hi All,

I have a dataset that I need to collapse by the id number because each 
ID has several rows (hhidnum). Mostly I just want to know the sum, 
because the variables are if a condition is present or absent (1/0) in 
the various rows for each ID.  Here is the code that I run:

*Collapse by HHID
    collapse (sum) segmentnum SBE_SEGLEN SBE_1A SBE_1B SBE_1C SBE_1D 
SBE_1E SBE_1F ///
    diSBE_12A diSBE_12B diSBE_12C diSBE_12D diSBE_12E diSBE_12F 
diSBE_12G diSBE_12H ///
    SBE_11A SBE_11B SBE_11C SBE_11D SBE_11E  littersmall litterhaz ///
    (mean) meanmph=SBE_5A meanlanes=SBE_7A ///
    by(hhidnum) cw

The error I get, though, is "factor variables not allowed". What does 
this mean? How do I get around it?

Thanks so much!

--
Lynne Morgan, MPH
Assistant Researcher
Survey of the Health of Wisconsin
University of Wisconsin, Madison
(e) lmorgan3@wisc.edu
(p) 608-821-1243

*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/