As Thomas suggested the solution is in the R-FAQ which is worth reading anyway:
as.numeric(as.character(old$q.D1)) < 0.05 If you try the above without the 'as.character()' you will see why this is necessary. -Christos -----Original Message----- From: Matthew Scholz [mailto:[EMAIL PROTECTED] Sent: Friday, March 10, 2006 7:41 PM To: [EMAIL PROTECTED] Cc: r-help@stat.math.ethz.ch Subject: Re: [R] newbie question: grouping rows Thanks for your response, Christos, but when I try this: > new = old[old$q.D1 < 0.05,] I get the following warning (and what I'm trying to do fails): Warning message: < not meaningful for factors in: Ops.factor(old$q.D1, 0.05) I've tried to bone up on the topic of factors and searching R help, but I'm still not sure why my data is being converted to that class nor do I know how to undo the conversion or work around it. Thanks again in advance of your advice. Any suggestions? Matt On 3/9/06, Christos Hatzis <[EMAIL PROTECTED]> wrote: > You can try: > > new.dataframe <- my.dataframe[my.dataframe$p.value < 0.05, ] > > This will select all columns. Alternatively, you can specify the > columns that you want after the ",". > > -Christos > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Matthew Scholz > Sent: Thursday, March 09, 2006 5:18 PM > To: r-help@stat.math.ethz.ch > Subject: [R] newbie question: grouping rows > > Hi all, > > I have a very simple question that I can't seem to find the answer to. > How do I extract rows that meet a certain criteria from a data frame > and group them into a new data frame? For example, if I want to make a > new data frame that only includes rows of data for which the p values > (given by one of the columns in the data frame) are less than a > certain value, how do I do this? It seems that there should be a > simple function that does this. I looked into getGroups from the nmle > package, but am not sure how to construct the form argument correctly > or even if it's the appropriate way to tackle this. > > Thanks in advance of your answer, > > Matt > > ______________________________________________ > R-help@stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > > > ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html