[R] Iterate over rows and update values based on condition

[arun]

Hi,
May be this helps:
dat1<- read.table(text="
id    user    action
1      12      login
2      12      view
3      12      view
4      12      view
5      12      login
6      12      view
7      12      view
8      12      login
",sep="",header=TRUE,stringsAsFactors=FALSE)


split(dat1,cumsum(dat1$action=="login"))
#$`1`
 # id user action
#1  1   12  login
#2  2   12   view
#3  3   12   view
#4  4   12   view
#
#$`2`
 # id user action
#5  5   12  login
#6  6   12   view
#7  7   12   view
#
#$`3`
 # id user action
#8  8   12  login
A.K.



----- Original Message -----
From: srecko joksimovic <sreckojoksimovic at gmail.com>
To: R-help at r-project.org
Cc: 
Sent: Tuesday, August 27, 2013 3:29 PM
Subject: [R] Iterate over rows and update values based on condition

Hi,

I have a data set with structure similar to this:
id    user    action
1      12      login
2      12      view
3      12      view
4      12      view
5      12      login
6      12      view
7      12      view
8      12      login

I want to create a list of sessions. That means to split table on every
occurrence of "login". Using Java (or some other language), I would
probably iterate through rows and create new List instance on every
"login", but I guess there is more efficient way to do that using R?

Thanks

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