# NOT RUN {
a <- as.ff(1:26)
b <- as.ff(factor(letters)) # vmode="integer"
c <- as.ff(factor(letters), vmode="ubyte")
df <- ffdf(a,b,c)
nrow(df) <- 2*26
df
message("NOTE that the new rows have silently the first level 'a' for UNSIGNED vmodes")
message("NOTE that the new rows have an illegal factor level <0> for SIGNED vmodes")
message("It is your responsibility to put meaningful content here")
message("As an example we replace the illegal zeros by NA")
df$b[27:52] <- NA
df
rm(a,b,c,df); gc()
# }
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