[R] selecting data from a data.frame?

[Prof Brian Ripley]

On 4 Jan 2002, Michael A. Miller wrote:

> I know how to plot a subset of a data.frame by doing something
> like
>
>  > plot( mydata$x[y>2] )
>
> Is there a way to do something similar for an entire data.frame?
> For example, I can do this something like
>
>  > lm( x[y>2] ~ type[y>2], data=mydata )
>
> but I'm a lazy typist, so I'd like to be able to do something
> like
>
>  > lm( x ~ type, data=mydata[y>2] )
>
> Is there a way to select rows from a data frame like that?

That will work if done correctly as mydata[y>2, ], but

lm(x ~ type, data=mydata, subset = (y>2))

is better style, especially as it allows y to be a column of mydata.


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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