On Apr 22, 2010, at 5:16 AM, Michael Haenlein wrote:
Dear all,
I have several character strings with a high number of different
levels.
unique(x) gives me values in the range of 100-200.
This creates problems as I would like to use them as predictors in a
coxph
model.
I therefore would like to convert each of these strings to a new
string
(x_new).
x_new should be equal to x for the top n categories (i.e. the top n
levels
with the highest occurrence) and NAN elsewhere.
For example, for n=3 x_new would have three levels: The three most
common
levels of x + NAN.
Is there some convenient way of doing this?
x <- sample(c("top", "three", "levels", "0ther", "strings"), 30,
replace=TRUE, prob=c(.3,.3,.3,.1,.1))
y <- c("top", "three", "levels")
xnew <- x
xnew[ !xnew %in% y ] <- "NAN" # not same as NaN
table(xnew)
#--------
xnew
levels NAN three top
5 5 9 11
--
David.
Thanks in advance,
Michael
Michael Haenlein
Associate Professor of Marketing
ESCP Europe
Paris, France
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