Message-ID: <83dca7860612252107j60f4836aq6cf3debc1dec4045@mail.gmail.com>
Date: 2006-12-26T05:07:57Z
From: Pedro Mardones
Subject: sequential row selection in dataframe
Dear all;
I'm wondering if there is any 'efficient' approach for selecting a
sample of 'every nth rows' from a dataframe. For example, let's use
the dataframe GAGurine in MASS library:
> length(GAGurine[,1])
[1] 314
# select an 75% of the dataset, i.e. = 236 rows, every 2 rows starting
from row 1
> test<-GAGurine[seq(1,314,2),]
> length(test[,1])
[1] 157
# so, I still need another 79 rows, one way could be:
test2<-GAGurine[-seq(1,314,2),]
> length(test2[,1])
[1] 157
> test3<-test2[seq(1,157,2),]
# and then
final<-rbind(test2,test3)
> length(final[,1])
[1] 236
Does anyone have a better idea to get the same results but without
creating different datasets like test2 and test3?
Thanks
PM