[R-sig-eco] keeping a variable as qualitative even if it is coded with numbers

[amelie_can]

Hello, 

I am running a fourthcorner analysis which links species abundance,
functionnal traits and environmental variable. One of my trait is about seed
dispersal (qualitative variable) in which I have four classes: wind, water,
short and long distance. One species can have many types of dispersal. So in
my original table, I created four different column. 

ex:  

       wind         water        short         long
sp1    1               1              0             0
sp2    0               0              1             0
sp3    0               1              1             1

and so forth. My problem is that those variable are considered as
quantitative but they are qualitative. 
I tried to transform them using the function as.factor but then it includes
the 0 in my analysis and I am not interest in that. 

Any ideas to make those variable "qualitative"?

Thank you all, 

Amelie
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