Hello,
It's not, in general, possible to fullfill the two constraints, to both
select 80% of the rows and to select all x %in% sampled x. Maybe the
following is a way close enough.
set.seed(244)
s <- sample(unique(dat$x), length(unique(dat$x))*0.8, prob = table(dat$x))
dat[dat$x %in% s,]
Hope this helps,
Rui Barradas
Em 21-11-2012 13:25, arun escreveu:
HI,
Your question is not very clear to me.
dat1<-data.frame(x=c(1,1,2,2,2,3,4,4),y=c(23,45,87,46,78,12,87,79))
If I select randomly 80% of data:
dat1[sample(nrow(dat1),0.8*nrow(dat1)),]
# x y
#4 2 46
#6 3 12
#7 4 87
#3 2 87
#2 1 45
#8 4 79
In this case, it is a mix of all the records that was in the original data.
So, if I understand correctly, then you want to get the original data, instead
of the 80% data (as you want all the records). But, suppose if the sample is:
set.seed(244)
dat2<-dat1[sample(nrow(dat1),0.8*nrow(dat1)),]
dat2
# x y
#2 1 45
#7 4 87
#8 4 79
#1 1 23
#5 2 78
#4 2 46
You wanted to eliminate the records 3 from the original dataset. Is that what
you meant?
If that is the case:
dat1[dat1$x%in%dat2$x,]
# x y
#1 1 23
#2 1 45
#3 2 87
#4 2 46
#5 2 78
#7 4 87
#8 4 79
A.K.
----- Original Message -----
From: Madhu Ganganapalli <mganganapa...@upstreamsoftware.com>
To: "r-help@r-project.org" <r-help@r-project.org>
Cc:
Sent: Wednesday, November 21, 2012 4:10 AM
Subject: Re: [R] FW: Select a random subset of rows out of matrix
Hi,
This is Madhu and I have a following doubt please give a solution...
**>i have the following data frame
from this i want to select a 80% of data randomly in such a way that
if the selected records are 1 and then we have to get the all records
corresponding to 1
similarly for 2 also and soon......... help me
data<-data.frame(x=c(1,1,2,2,2,3,4,4,4),y=c(23,45,87,46,78,12,87,79));**
Regards,
Madhu.
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