[R] adding columns to dataframes contained in a list

From: E Hofstadler <e.hofstadler_at_gmail.com>
Date: Wed, 04 May 2011 10:25:06 +0300


hi there,

I have a list of 5 identical dataframes:

mydf <- data.frame(x=c(1:5), y=c(21:25)) mylist <- rep(list(mydf),5)

and a factor variable with 5 levels:

foo <- c(letters[1:5])
foo <- as.factor(foo)

Question:
I'd like to add a new variable to each dataframe in the list, each containing only one level of the factor variable. So mylist[[1]] should have a new variable z containing only "a", in mylist[[2]] the new variable z should contain only "b", etc.

(How) can this be done without looping?

All help is greatly appreciated.

Best,
Esther



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