R help - May 2000 - extracting a sub data frame by value of one of its columns

Dear R people,

This should be a straightforward operation, but I am having difficulties.
I have a data frame with three columns, call them a, b, and c. c is a
column of factors, 1...10. I want to extract all the rows for which c has
the value say 1, and put them in a separate data frame. I looked at the
various sort functions provided, but see no way to easily adapt them to my
needs.
                                   Sincerely, Faheem Mitha.

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On Sun, 7 May 2000, Faheem Mitha wrote:
> Dear R people,
> 
> This should be a straightforward operation, but I am having difficulties.
> I have a data frame with three columns, call them a, b, and c. c is a
> column of factors, 1...10. I want to extract all the rows for which c has
> the value say 1, and put them in a separate data frame. I looked at the
> various sort functions provided, but see no way to easily adapt them to my
> needs.
Nothing to do with sorting as far as I can see. Try

df2 <- df1[df1$c == 1,]

and note that indexing is pretty central to using S (the language), so it
is worth learning all the ways to use it.


-- 
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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