[R] variable (column) in a data frame

[peter dalgaard]

On Jul 15, 2012, at 17:41 , Paulo Barata wrote:

> 
> Dr. Dalgaard,
> 
> Thank you. But pre-checking with is.null() or using with()
> doesn't solve the problem of catching spelling mistakes
> in the name of a variable inside a data frame, when using 
> the df$var notation often in a program.
> 
> Is there some way for R to behave, in relation to a variable 
> inside a data frame, the same way it behaves for a variable 
> not in a data frame? For example:

You could try reading the 2nd half of my one-line reply....

>> 
>> You can pre-check for is.null(df$aaa) or use with(df, sum(aaa==2)).

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com