[R] Removing objects from a list based on nrow

[Tim Clark]

Jim,

Good catch!  I know in my current problem there are objects with less than 3 rows, but will make sure to modify the function for future use.

Thanks,

Tim


Tim Clark
Department of Zoology 
University of Hawaii


--- On Sun, 11/29/09, Linlin Yan <yanlinlin82 at gmail.com> wrote:

> From: Linlin Yan <yanlinlin82 at gmail.com>
> Subject: Re: [R] Removing objects from a list based on nrow
> To: "jim holtman" <jholtman at gmail.com>
> Cc: "Tim Clark" <mudiver1200 at yahoo.com>, r-help at r-project.org
> Date: Sunday, November 29, 2009, 4:35 AM
> Thank Jim! You are right. I didn't
> notice the case of none of rows
> match the condition.
> 
> On Sun, Nov 29, 2009 at 10:10 PM, jim holtman <jholtman at gmail.com>
> wrote:
> > One thing to be careful of is if no dataframe have
> less than 3 rows:
> >
> >>
> df1<-data.frame(letter=c("A","B","C","D","E"),number=c(1,2,3,4,5))
> >>
> df2<-data.frame(letter=c("A","B"),number=c(1,2))
> >>
> df3<-data.frame(letter=c("A","B","C","D","E"),number=c(1,2,3,4,5))
> >>
> df4<-data.frame(letter=c("A","B","C","D","E"),number=c(1,2,3,4,5))
> >>
> >> lst<-list(df1,df3,df4)
> >> lst
> > [[1]]
> >  letter number
> > 1      A      1
> > 2      B      2
> > 3      C      3
> > 4      D      4
> > 5      E      5
> >
> > [[2]]
> >  letter number
> > 1      A      1
> > 2      B      2
> > 3      C      3
> > 4      D      4
> > 5      E      5
> >
> > [[3]]
> >  letter number
> > 1      A      1
> > 2      B      2
> > 3      C      3
> > 4      D      4
> > 5      E      5
> >
> >> lst[-which(sapply(lst, nrow) < 3)]
> > list()
> >>
> >
> > Notice the list is now empty.  Instead use:
> >
> >> lst[sapply(lst, nrow) >=3]
> > [[1]]
> >  letter number
> > 1      A      1
> > 2      B      2
> > 3      C      3
> > 4      D      4
> > 5      E      5
> >
> > [[2]]
> >  letter number
> > 1      A      1
> > 2      B      2
> > 3      C      3
> > 4      D      4
> > 5      E      5
> >
> > [[3]]
> >  letter number
> > 1      A      1
> > 2      B      2
> > 3      C      3
> > 4      D      4
> > 5      E      5
> >
> >
> > On Sun, Nov 29, 2009 at 3:43 AM, Linlin Yan <yanlinlin82 at gmail.com>
> wrote:
> >> Try these:
> >> sapply(lst, nrow) # get row numbers
> >> which(sapply(lst, nrow) < 3) # get the index of
> rows which has less than 3 rows
> >> lst <- lst[-which(sapply(lst, nrow) < 3)] #
> remove the rows from the list
> >>
> >> On Sun, Nov 29, 2009 at 4:36 PM, Tim Clark <mudiver1200 at yahoo.com>
> wrote:
> >>> Dear List,
> >>>
> >>> I have a list containing data frames of
> various numbers of rows.  I need to remove any data frame
> that has less than 3 rows.  For example:
> >>>
> >>>
> df1<-data.frame(letter=c("A","B","C","D","E"),number=c(1,2,3,4,5))
> >>>
> df2<-data.frame(letter=c("A","B"),number=c(1,2))
> >>>
> df3<-data.frame(letter=c("A","B","C","D","E"),number=c(1,2,3,4,5))
> >>>
> df4<-data.frame(letter=c("A","B","C","D","E"),number=c(1,2,3,4,5))
> >>>
> >>> lst<-list(df1,df2,df3,df4)
> >>>
> >>> How can I determine that the second object
> (df2) has less than 3 rows and remove it from the list?
> >>>
> >>> Thanks!
> >>>
> >>> Tim
> >>>
> >>>
> >>>
> >>>
> >>> Tim Clark
> >>> Department of Zoology
> >>> University of Hawaii
> >>>
> >>>
> ______________________________________________
> >>> 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.
> >>>
> >>
> >> ______________________________________________
> >> 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.
> >>
> >
> >
> >
> > --
> > Jim Holtman
> > Cincinnati, OH
> > +1 513 646 9390
> >
> > What is the problem that you are trying to solve?
> >
>