[R] if a variable is defined

[Bill.Venables at csiro.au]

!is.null(my.object at my.data.frame$my.var) 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Kushan Thakkar
Sent: Friday, 11 February 2011 10:30 AM
To: r-help at r-project.org
Subject: [R] if a variable is defined

I have an object type my.object. One of its slots contains a data frame
(i.e. my.object at my.data.frame) .. I want to check if one of the variables
exists in this data frame (i.e. my.object at my.data.frame$my.var)

I am trying to use the exists function but can't figure out how the
arguments work. Please help.

So far I have tried

exists(my.object at my.data.frame$my.var)
exists("my.object at my.data.frame$my.var")
exists("my.var",where="my.object at my.data.frame")

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