Colin, Unless I missed something, the head function doesn't sort. So if I have 1000 values that match, head just gives me the first three, not the HIGHEST three.
[df.mydata$A=="X"& df.mydata$C< 2, On 8/26/09 3:01 AM, Colin Millar wrote: > Hi, > > This should work - head is quite a usefull summary function > > head(df.mydata[df.mydata$A=="X"& df.mydata$C< 2, ],3) > > > Colin. > > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] > On Behalf Of Noah Silverman > Sent: 26 August 2009 10:54 > To: ottorino-luca.pant...@unifi.it > Cc: r help > Subject: Re: [R] Select top three values from data frame > > > I only have a few values in my example, but the real data set might have > > 20-100 rows with A="X". So how do I pick just the three highest ones? > > -N > > > On 8/26/09 2:46 AM, Ottorino-Luca Pantani wrote: > >> df.mydata[df.mydata$A=="X" AND df.mydata$C< 2, ] >> will do the job ? >> >> 8rino >> >> Noah Silverman ha scritto: >> >>> Hi, >>> >>> I'm trying to find an easy way to do this. >>> >>> I want to select the top three values of a specific column in a >>> subset of rows in a data.frame. I'll demonstrate. >>> >>> A B C >>> x 2 1 >>> x 4 1 >>> x 3 2 >>> y 1 5 >>> y 2 6 >>> y 3 8 >>> >>> >>> I want the top 3 values of B from the data.frame where A=X and C<2 >>> >>> I could extract all the rows where C<2, then sort by B, then take the >>> > >>> first 3. But that seems like the wrong way around, and it also will >>> get messy with real data of over 100 columns. >>> >>> Any suggestions? >>> >>> > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide > http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________________________________ > This email has been scanned by the MessageLabs Email Security System. > For more information please visit http://www.messagelabs.com/email > ______________________________________________________________________ > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
