## this is often not intended
as.numeric(factor(c(5,7))) ## result: c(1,2)
## but this
fac2num(factor(c(5,7))) ## result: c(5,7)
## however
as.numeric(factor(c("5","7","a"))) ## 1:3
suppressWarnings(
fac2num(factor(c("5","7","a"))) ## c(5,7,NA)
)
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