[R] agrep confusion

[Paul Galpern]

I am sure there is something I am just not understanding about agrep 
functionality. 

str1 <- c("ab","aba","abc")
agrep("abc",str1, max.distance = list(insertions=0, substitutions=0, 
deletions=1), value=T)

returns:
[1] "ab"  "aba" "abc"

Why is "aba" a match?  It seems to me that this should require a 
substitution and this has been set to 0 in max.distance.  Alternatively 
this would require a deletion plus an insertion but, again, not 
permitted in arguments.

Thanks for your help,

Paul Galpern
PhD Candidate
Natural Resources Institute
University of Manitoba
Winnipeg, Manitoba, Canada