Negative Data Error with Decorana in Vegan

I'm fairly inexperienced with the Vegan package, so my apologies if I'm 
asking a very basic question.  I'm trying to use the decorana function 
in the Vegan package.  My data is all positive numbers but I get an 
error that says this:

Error in decorana(dataord) :
   'decorana' cannot handle negative data entries

The data (dataord) is of class data.frame and originated from an SQLite 
database brought into R using the RSQLite package, just in case those 
details matter.  I'm fairly sure that the numbers in the data frame are 
numbers and not text, but if they were text, would that cause the error?

Any ideas what is causing the problem or how to get around it?  Thank you!

best,
Michele

Michele Tobias

PhD Candidate
Geography Graduate Group
University of California, Davis

mmtobias at ucdavis.edu
http://ucdavis.academia.edu/MicheleTobias