[R] Understanding cenros Error

[Rich Shepard]

   Before reading water chemistry into a data frame I removed all missing
data. Yet when I try to run cenros() to summarize a specific chemical I get
an error that I do not understand:

with( subset(chem, param=='Ag'),  cenros(quant,ceneq1) )
Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) :
   NA/NaN/Inf in 'y'

   I would like to learn what I did incorrectly so I can avoid these errors
in the future.

   The data frame structure is

str(chem)
'data.frame':	120309 obs. of  8 variables:
  $ site    : Factor w/ 65 levels ";Influent","D-1",..: 2 2 2 2 2 2 ...
  $ sampdate: Date, format: "2007-12-12" "2007-12-12" ...
  $ preeq0  : logi  TRUE TRUE TRUE TRUE TRUE TRUE ...
  $ param   : Factor w/ 37 levels "Ag","Al","Alk_tot",..: 1 2 8 17 3 9 ...
  $ quant   : num  0 0.106 1 231 231 0.011 0 0.002 0 100 ...
  $ ceneq1  : logi  FALSE FALSE TRUE FALSE FALSE FALSE ...
  $ floor   : num  0 0.106 0 231 231 0.011 0 0 0 100 ...
  $ ceiling : Factor w/ 3909 levels "0.000","0.000)",..: 1 116 841 1771 ...

   I ran dput() on the data frame but cannot make sense of the output (a 5.5M
ASCII text file).

   Pointers appreciated.

Rich