[R] subsetting a data.frame to the 'unique' of a column

Rudi Alberts r.alberts at rug.nl
Thu Dec 23 20:28:31 CET 2004


I often run into this problem:
I have a data.frame with one column containing entries that are not
unique. What I then want is a subset of the data.frame in which
the entries in that column have become the 'unique' of the original
Normally I program around it by taking the unique of the column and
making a new data.frame with it and filling the rest of the data.

(By the way, when moving to the smaller data.frame for example 5 rows
with the same value in that column will be replaced by one row for that
value. I don't mind which of the rows now..)

something like this, however, this gives me the complete df.

df[df$colname %in% unique(df$colname),]

or this, which doesnt work

df[df$colname == unique(df$colname),]

regards, R. Alberts

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