data("NELS88")
str(NELS88)
ftable(xtabs(~ Urban+Rural + Public, NELS88))#
## Add more sensible variable, ordered factor rural < agglo < urban
NELS88. <- within(NELS88, {
UR <- factor(Urban:Rural, labels = c("agglo", "rural", "urban"))
Urbanity <- ordered(UR, levels = c("rural", "agglo", "urban"))
rm(UR) })
unique(NELS88.[, c("Urban","Rural", "Urbanity")]) # indeed, just 3 combination cases
xtabs(~ Minority+Urbanity, NELS88.) # (_not_ independent)
ftable(xtabs(~ Public+Urbanity+Female+Minority, NELS88.) -> tab.)
summary(tab.) # very very clearly not independent
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