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

Mikkel Grum mi2kelgrum at yahoo.com
Fri Jul 8 16:16:57 CEST 2005

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:

aa <- iris[1:101,]

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

setosa versicolor  virginica 
        50         50          1 

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


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,

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