Removing objects from a list based on nrow

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
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

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Removing objects from a list based on nrow

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