parsing protocol of states

Dear R-users,

actually i try to parse some state protocols for my work. i an easy 
stetting the code below works fine, if states are reached only once. in 
harder settings it could be possible that one state gets visited more 
times. in this case for me its interesting to see how much waiting time 
lies between to states on the whole.

by the way i didn't use R as a parsing tool so far, so any advice for 
doing this more effectivly are quite welcome.

str01 <- "2007-10-12 11:50:05 state B. ,2007-10-12 11:50:05 state C. 
,2007-10-12 13:23:24 state D. ,2007-10-12 13:23:43 state E. ,2007-10-14 
15:43:19 state F. ,2007-10-14 15:43:20 state E. ,2007-10-14 15:43:25 
state G. ,2007-10-14 15:43:32 state H. ,2007-10-14 15:43:41 state I. 
,2007-10-14 15:43:47 state F. ,2007-10-14 15:43:47 state G. ,2007-10-14 
15:48:08 state H. ,2007-10-16 10:10:20 state J. ,2007-10-19 11:12:54 
state K ,2007-10-19 11:17:37 state D. ,2007-10-19 11:17:42 state E. 
,2007-10-19 11:17:49 state F. ,2007-10-19 11:17:51 state E. ,2007-10-19 
11:17:58 state H. ,2007-10-19 11:18:05 state J. ,2007-10-19 11:21:45 
state L."

str02 <- unlist(strsplit(str01, "\\,"))

x1 <- grep("state B", str02)
x2 <- grep("state C", str02)
x3 <- grep("state D", str02)
x4 <- grep("state E", str02)
x5 <- grep("state F", str02)
x6 <- grep("state G", str02)
x7 <- grep("state H", str02)
x8 <- grep("state I", str02)
x9 <- grep("state J", str02)
x10 <- grep("state K", str02)
x11 <- grep("state L", str02)

t1 <- substr(str02[x1], 1, 19)
t1 <- as.POSIXct(strptime(t1, "%Y-%m-%d %H:%M:%S"))
t2 <- substr(str02[x2], 1, 19)
t2 <- as.POSIXct(strptime(t2, "%Y-%m-%d %H:%M:%S"))
t3 <- substr(str02[x3], 1, 19)
t3 <- as.POSIXct(strptime(t3, "%Y-%m-%d %H:%M:%S"))
t4 <- substr(str02[x4], 1, 19)
t4 <- as.POSIXct(strptime(t4, "%Y-%m-%d %H:%M:%S"))
t5 <- substr(str02[x5], 1, 19)
t5 <- as.POSIXct(strptime(t5, "%Y-%m-%d %H:%M:%S"))
t6 <- substr(str02[x6], 1, 19)
t6 <- as.POSIXct(strptime(t6, "%Y-%m-%d %H:%M:%S"))
t7 <- substr(str02[x7], 1, 19)
t7 <- as.POSIXct(strptime(t7, "%Y-%m-%d %H:%M:%S"))
t8 <- substr(str02[x8], 1, 19)
t8 <- as.POSIXct(strptime(t8, "%Y-%m-%d %H:%M:%S"))
t9 <- substr(str02[x9], 1, 19)
t9 <- as.POSIXct(strptime(t9, "%Y-%m-%d %H:%M:%S"))
t10 <- substr(str02[x10], 1, 19)
t10 <- as.POSIXct(strptime(t10, "%Y-%m-%d %H:%M:%S"))
t11 <- substr(str02[x11], 1, 19)
t11 <- as.POSIXct(strptime(t11, "%Y-%m-%d %H:%M:%S"))

as.numeric(difftime(t11, t1, units="days"))

## waiting times between state E and F
sum(as.numeric(difftime(t5, t4, units="days")))


best regards

Andreas