[R] Inserting Missing Data

[Kurt_Helf at nps.gov]

Greetings
     I'm attempting to insert missing data on the smallest size class of
cave cricket instars into a data frame. The data involve censusing
photoplots (plots) of roosting cave crickets in which we discern in four
instars or size classes.  I need to insert data on size class one into a
data frame that already has data on size classes two through four.  The
data can be merged by their cave name, year, month, region (near or far
from cave entrance), plot #, and Individual (IndID).  For example:
(Embedded image moved to file: pic14606.jpg)

As one example, I have data for size class (SC) one I can insert after
IndID #4 in the data above.  However, when I attempt to merge these two
data frames using the following commands:
"Hs.full.anal<-merge(Hs.short.missgval,SC1_0608,
      byx=c(Cave,Year,Month,Region,Plot,IndID),
      byy=c(Cave,Year,Month,Region,Plot,IndID))"
I get the following message:
"WARNING: Warning in `[<-.factor`(`*tmp*`, ri, value = c(1L, 1L, 1L, 1L,
1L, 1L, 1L,  :
  invalid factor level, NAs generated"

Can anyone tell me what this means and how I might fix it?
Cheers
Kurt

***************************************************************
Kurt Lewis Helf, Ph.D.
Ecologist
EEO Counselor
National Park Service
Cumberland Piedmont Network
P.O. Box 8
Mammoth Cave, KY 42259
Ph: 270-758-2163
Lab: 270-758-2151
Fax: 270-758-2609
****************************************************************
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CUPN Forest Pest Monitoring Website:
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