Hello All, I have a list of dataframes, and I need to subset it by keeping only those dataframes in the list that meet a certain criterion. Specifically, I need to generate a second list which only includes those dataframes whose number of rows is > 1. Could someone suggest how to do this? I have come close to what I need with loops and such, but there must be a less clumsy way... Many thanks, Lara [[alternative HTML version deleted]]
Hi Lara, You might try the following (untested): yourlistofdataframes[sapply(yourlistofdataframes, function(d) nrow(d) > 1)] HTH, Jorge On Tue, May 17, 2011 at 4:24 PM, Lara Poplarski <> wrote:> Hello All, > > I have a list of dataframes, and I need to subset it by keeping only those > dataframes in the list that meet a certain criterion. Specifically, I need > to generate a second list which only includes those dataframes whose number > of rows is > 1. > > Could someone suggest how to do this? I have come close to what I need with > loops and such, but there must be a less clumsy way... > > Many thanks, > Lara > > [[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. >[[alternative HTML version deleted]]
shouldKeep <- sapply(listOfDataFrames, function(df)nrow(df)>1) listOfDataFrames[shouldKeep] or, compressed to get rid of the intermediate variable listOfDataFrames[sapply(listOfDataFrames, function(df)nrow(df)>1)] If you are writing production code and there is any chance that listOfDataFrames might be an empty list you can use vapply (which requires that you supply a prototype for FUN's return value): listOfDataFrames[vapply(listOfDataFrames, function(df)nrow(df)>1, FUN.VALUE=FALSE)] Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com> -----Original Message----- > From: r-help-bounces at r-project.org > [mailto:r-help-bounces at r-project.org] On Behalf Of Lara Poplarski > Sent: Tuesday, May 17, 2011 1:25 PM > To: r-help at r-project.org > Subject: [R] subsetting a list of dataframes > > Hello All, > > I have a list of dataframes, and I need to subset it by > keeping only those > dataframes in the list that meet a certain criterion. > Specifically, I need > to generate a second list which only includes those > dataframes whose number > of rows is > 1. > > Could someone suggest how to do this? I have come close to > what I need with > loops and such, but there must be a less clumsy way... > > Many thanks, > Lara > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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. >
On 18/05/11 08:24, Lara Poplarski wrote:> Hello All, > > I have a list of dataframes, and I need to subset it by keeping only those > dataframes in the list that meet a certain criterion. Specifically, I need > to generate a second list which only includes those dataframes whose number > of rows is> 1. > > Could someone suggest how to do this? I have come close to what I need with > loops and such, but there must be a less clumsy way...L.new <- L[tapply(L,nrow) > 1] cheers, Rolf Turner
Have a look at lapply(). Something like: entries.with.nrows=lapply(data,function(x)dim(x)[1]>1) should give you a vector with the elements of the list that you seek marked with TRUE. This vector can then be used to extract a subset from your list by: data.reduced=data[entries.with.nrows] Or similar.... HTH Jannis --- Lara Poplarski <larapoplarski at gmail.com> schrieb am Di, 17.5.2011:> Von: Lara Poplarski <larapoplarski at gmail.com> > Betreff: [R] subsetting a list of dataframes > An: r-help at r-project.org > Datum: Dienstag, 17. Mai, 2011 20:24 Uhr > Hello All, > > I have a list of dataframes, and I need to subset it by > keeping only those > dataframes in the list that meet a certain criterion. > Specifically, I need > to generate a second list which only includes those > dataframes whose number > of rows is > 1. > > Could someone suggest how to do this? I have come close to > what I need with > loops and such, but there must be a less clumsy way... > > Many thanks, > Lara > > ??? [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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. >