[R] subset arg in subset(). was: converting result of substitute to 'ordidnary' expression

[Vadim Ogranovich]

Dear R users,

Please disregard my previous post "converting result of substitute to 'ordidnary' expression". The problem I have has nothing to do with substitute.

Consider:

> dat <- data.frame(x=1:10, y=1:10)

> subsetexp <- expression(5<x)

> ## this does work
> subset(dat, eval(subsetexp))
    x  y
6   6  6
7   7  7
8   8  8
9   9  9
10 10 10

> ## and so does this
> subset(dat, 5<x)
    x  y
6   6  6
7   7  7
8   8  8
9   9  9
10 10 10

> ## but this doesn't work
> subset(dat, subsetexp)
Error in subset.data.frame(dat, subsetexp) :
  'subset' must evaluate to logical

Why did the last expression fail and why it worked with eval()?

Thank you very much for your help,
Vadim

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