[R] removing factor level represented by less than x rows

From: Mikkel Grum <mi2kelgrum_at_yahoo.com>
Date: Sat 09 Jul 2005 - 00:16:57 EST


In a number of different situations I'm trying to remove factor levels that are represented by less than a certain number of rows, e.g. if I had the dataset aa below and wanted to remove the species that are represented in less than 2 rows:

data(iris)
aa <- iris[1:101,]

In this case, since I can see that the species virginica only has one row, I can write:

table(aa$Species)
setosa versicolor virginica

        50 50 1

aa[aa$Species != "virginica", ]

but:

aa[aa$Species == names(table(aa$Species)> 2),]

does not work.

This must be a fairly common task with a straight forward solution that I can't see. Any ideas?

Best wishes,
Mikkel



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