[R] Select the last rows of when specific conditions are met.

[arun]

HI,

Instead of splitting, you could also do this:
dat1<-read.table(text="
Subj Trial  tt  
1          1      1    
1          1      2    
1          1      3    
1          1      4     
1          1      5     
1          2      1     
1          2      2     
1          2      3     
1          3      1     
1          3      2     
1          3      3     
2          1      1     
2          1      2     
2          1      3
",sep="",header=TRUE)  


dat2<-dat1[as.logical(ave(dat1$tt,list(dat1$Subj,dat1$Trial),FUN=function(x) x<4)),]
 dat2
#   Subj Trial tt
#1     1     1  1
#2     1     1  2
#3     1     1  3
#6     1     2  1
#7     1     2  2
#8     1     2  3
#9     1     3  1
#10    1     3  2
#11    1     3  3
#12    2     1  1
#13    2     1  2
#14    2     1  3
A.K.










----- Original Message -----
From: mardijk <van_dijkmarianne at hotmail.com>
To: r-help at r-project.org
Cc: 
Sent: Thursday, November 1, 2012 11:18 AM
Subject: [R] Select the last rows of when specific conditions are met.

Hello,

As I am new with R I am completely stuck in resolving a, no doubt, easy
problem.

I have a dataset with an enormous amount of rows and 17 columns. I need to
know per trial and subject number if another variable (tt) exceeds a
maximum. If this is true than the last 5000 rows of that specific trial for
that subject number needs to be deleted. 

But I am completely stuck on how to do so. After various attempts I have
finally come up with the following (which obviously does not work).


if (dat["tt"]>6000
){
    return(
    tail(dattest[,c("Trial", "Subj" )],n=5000) <- NA
}

Can anybody explain what I need to do?

Thank you so much!






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