[R] dataframe subset

[Chuck Cleland]

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.
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