## default symbols:
abc(26)
rfree(1,10)
# if we need more than 26:
options(symbols=state.name)
rfree(10,4)
# or even:
jj <- letters[1:10]
options(symbols=apply(expand.grid(jj,jj),1,paste,collapse=""))
rfree(10,10,100,4)
options(symbols=NULL) # NULL is interpreted as letters a-z
rfree(10,4) # back to normal
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