Re: [R] dataframe subset

From: Chuck Cleland <ccleland_at_optonline.net>
Date: Thu 09 Feb 2006 - 01:48:51 EST

Bernhard Baumgartner wrote:
> I have a dataframe with a column, say "x" consisting of values, each
> value appearing different times, e.g.
> x: 1,1,1,1,2,2,4,4,4,9,10,10,10,10,10 ...
> and a vector, including e.g.:
> y: 2,9,10,...
> I need a subset of the dataframe: all rows where x is equal to one of
> the values in y. Currently I use a loop for this, but because x and y
> are large this is very slow.
> Is there any idea how to solve this problem faster?

mydata <- data.frame(X = sample(1:10, 10000, replace=TRUE),

                      Y = sample(c(2,9,10), 10000, replace=TRUE))

newdata <- mydata[mydata$X %in% unique(mydata$Y),]

?"%in%"

-- 
Chuck Cleland, Ph.D.
NDRI, Inc.
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New York, NY 10010
tel: (212) 845-4495 (Tu, Th)
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Received on Thu Feb 09 03:36:02 2006

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