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

[Vadim Ogranovich]

It does work, thank you, but the literal 5<x now needs to be quoted by expression():

> do.call(subset, list(dat, expression(5<x)))
    x  y
6   6  6
7   7  7
8   8  8
9   9  9
10 10 10

This is ok, but the standard "subset(dat, 5<x)" looks more readable.

Anyway, thank you for your help, it's a nice paradigm.

Vadim

-----Original Message-----
From: Bill.Venables at csiro.au [mailto:Bill.Venables at csiro.au]
Sent: Saturday, June 26, 2010 1:08 AM
To: Vadim Ogranovich; r-help at r-project.org
Subject: RE: [R] subset arg in subset(). was: converting result of substitute to 'ordidnary' expression

Here is another one that works:

> do.call(subset, list(dat, subsetexp))
    x  y
6   6  6
7   7  7
8   8  8
9   9  9
10 10 10
>



-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Vadim Ogranovich
Sent: Saturday, 26 June 2010 11:13 AM
To: 'r-help at r-project.org'
Subject: [R] subset arg in subset(). was: converting result of substitute to 'ordidnary' expression

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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