[R] Condition to factor (easy to remember)

[Dieter Menne]

Dear List,

creating factors in a given non-default orders is notoriously difficult to
explain in a course. Students love the ifelse construct given below most,
but I remember some comment from Martin Mächler (?) that ifelse should be
banned from courses.

Any better idea? Not necessarily short, easy to remember is important.

Dieter


data = c(1,7,10,50,70)
levs = c("Pre","Post")

# Typical C-Programmer style
factor(levs[as.integer(data >10)+1], levels=levs)

# Easiest to understand
factor(ifelse(data <=10, levs[1], levs[2]), levels=levs)

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