On Aug 18, 2011, at 10:27 AM, B Jessop wrote:
Dear r-help,
I would like to select a subset of levels from a factor variable in
a data frame and return a data frame.
The data set consists of 3 variables, 2 of which are factors (Site,
Fish) and one numeric (Datavalue) as follows:
Site Fish Datavalue
AB 2-1 2.3
AB 2-1 2.4
AB 2-1 2.2
AB 2-2 2.6
AB 2-2 2.5
AB 2-2 2.7
AB 2-3 1.6
AB 2-3 1.5
AB 2-3 1.4
etc
AB 2-20 3.1
AB 2-20 2.9
AB 2-20 3.0
I would like to create a subset containing all variable rows but for
only, say, Fish 2-1, 2-2, and 2-3. The following code:
subset(Df1, Fish %in% c("2-1", "2-2", "2-3")
factors are not ordered (by default anyway) so the ":" (seq) operator
has no meaning;
Df2 <- subset(Df1, Eel=="2-1" | Eel=="2-3") selects only Eel 2-1 and
2-3. The use of a ":" rather than "|" gives an error message. My
other approaches did not work. Any
Eel? What????
suggestions for doing this task would be much appreciated.
Regards,
BJ
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David Winsemius, MD
West Hartford, CT
______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
