help on Nan error

When i want to do ANOSIM i get an NaN error message. What is wrong?

(lots of other code)
iwithin=rep(0,(N*(N-1)/2) )
r.w=sum(r*iwithin)/sum(iwithin)

iwithin is a vector of zeroes and so is its sum.  r*iwithin is also a 
vector of zeroes, and so is its sum.  Thus r.w=sum(r*iwithin)/sum(iwithin) 
is zero divided by zero, which is not defined.

Regards,
Richie.

Mathematical Sciences Unit
HSL


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