On Jan 30, 2010, at 4:09 PM, david hilton shanabrook wrote:
I have a data frame with two columns, a factor and a numeric. I
want to create data frame with the factor, its frequency and the
median of the numeric column
head(motifList)
events score
1 aeijm -0.25000000
2 begjm -0.25000000
3 afgjm -0.25000000
4 afhjm -0.25000000
5 aeijm -0.25000000
6 aehjm 0.08333333
To get the frequency table of events:
motifTable <- as.data.frame(table(motifList$events))
head(motifTable)
Var1 Freq
1 aeijm 110
2 begjm 46
3 afgjm 337
4 afhjm 102
5 aehjm 190
6 adijm 18
Now get the score column back in.
motifTable2 <- merge(motifList, motifTable, by="events")
head(motifTable2)
events percent freq
1 adgjm 0.00000000 111
2 adgjm NA 111
3 adgjm 0.13333333 111
4 adgjm 0.06666667 111
5 adgjm -0.16666667 111
6 adgjm NA 111
Then lastly to aggregate on the events column getting the median of
the score
motifTable3 <- aggregate.data.frame(motifTable2,
by=list(motifTable2$events), FUN=median, na.rm=TRUE)
Error in median.default(X[[1L]], ...) : need numeric data
Which gives the error as events are a factor. Can someone enlighten
me to a more obvious approach?
I don't think grouping on a factor is the source of your error. You
have NA's in your data and median will choke on those unless you
specify na.rm=TRUE.
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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