How I can find out 1st and last observation with in group in R for every by group

Question

Hi my data set is as follows

dialled     Ringing     state   duration
NA  NA  NA  0
NA  NA  NA  0
NA  NA  NA  0
NA  NA  NA  0
123 NA  NA  0
123 NA  NA  0
123 NA  NA  0
123 NA  NA  60
NA  NA  active  0
NA  NA  active  0
NA  NA  inactive    0
NA  NA  inactive    0
NA  145 inactive    0
NA  145 inactive    0
NA  145 inactive    56
NA  NA  active  0
NA  NA  active  0
NA  NA  inactive    0
222 NA  inactive    0
222 NA  inactive    0
222 NA  inactive    37
NA  NA  active  0
NA  NA  active  0
NA  NA  inactive    0
123 NA  inactive    0
123 NA  inactive    0
123 NA  active  60
NA  NA  active  0

I want to get 1st and last obs. for every dialled number (repeated one as well, because every call is different). Answer I am looking for is

dialled     Ringing     state   duration
123 NA  NA  0
123 NA  NA  60
222 NA  inactive    0
222 NA  inactive    37
123 NA  NA  0
123 NA  NA  60   

I was using the following

library(plyr)
ddply(DF, .(Dialled_nbr), function(x) x[c(1,nrow(x)), ]) which gave me

dialled     Ringing     state   duration
123 NA  NA  0
123 NA  NA  60
222 NA  inactive    0
222 NA  inactive    37

But answer is not correct. Please help

New data is

dialled     Ringing     state   duration
123 NA  NA  0
123 NA  NA  0
123 NA  NA  60
123 NA  NA  0
123 NA  NA  0
123 NA  NA  70
222 NA  inactive    0
222 NA  inactive    0
222 NA  inactive    37
123 NA  inactive    0
123 NA  inactive    0
123 NA  active  60


Answer to be
dialled     Ringing     state   duration
123 NA  NA  0
123 NA  NA  60
123 NA  NA  0
123 NA  NA  70
222 NA  inactive    0
222 NA  inactive    37
123 NA  inactive    0
123 NA  active  60

Answer 1

Here is an option with data.table_1.9.5. Create the "data.table" from "data.frame" using setDT, remove the NA values in "dialled" column (!is.na(dialled)), generate grouping variable by using rleid on "Dialled_nbr", get the row index of the first and last rows for the levels of grouping variable (.I(c(1L, .N)]), finally subset the "dt1" based on the row index.

library(data.table)
dt1 <- setDT(df)[!is.na(dialled)]
dt1[dt1[,.I[c(1L, .N)],rleid(dialled)]$V1]
#    dialled Ringing    state duration
#1:     123      NA       NA        0
#2:     123      NA       NA       60
#3:     222      NA inactive        0
#4:     222      NA inactive       37
#5:     123      NA inactive        0
#6:     123      NA   active       60

Or using base R

df1 <- df[!is.na(df$dialled),]
grp<-  inverse.rle(within.list(rle(df1$dialled), 
                    values <- seq_along(values)))

df1[!duplicated(grp)|!duplicated(grp,fromLast=TRUE),]
#    dialled Ringing    state duration
#5      123      NA     <NA>        0
#8      123      NA     <NA>       60
#19     222      NA inactive        0
#21     222      NA inactive       37
#25     123      NA inactive        0
#27     123      NA   active       60

Update

Based on the new dataset,

grp <- cumsum(c(TRUE,df$duration[-nrow(df)]!=0))
df[!duplicated(grp)|!duplicated(grp,fromLast=TRUE),]
#   dialled Ringing    state duration
#1      123      NA     <NA>        0
#3      123      NA     <NA>       60
#4      123      NA     <NA>        0
#6      123      NA     <NA>       70
#7      222      NA inactive        0
#9      222      NA inactive       37
#10     123      NA inactive        0
#12     123      NA   active       60

data

 df <- structure(list(dialled = c(NA, NA, NA, NA, 123L, 123L, 123L, 
 123L, NA, NA, NA, NA, NA, NA, NA, NA, NA, NA, 222L, 222L, 222L, 
 NA, NA, NA, 123L, 123L, 123L, NA), Ringing = c(NA, NA, NA, NA, 
 NA, NA, NA, NA, NA, NA, NA, NA, 145L, 145L, 145L, NA, NA, NA, 
 NA, NA, NA, NA, NA, NA, NA, NA, NA, NA), state = c(NA, NA, NA, 
 NA, NA, NA, NA, NA, "active", "active", "inactive", "inactive", 
 "inactive", "inactive", "inactive", "active", "active", "inactive", 
 "inactive", "inactive", "inactive", "active", "active", "inactive", 
 "inactive", "inactive", "active", "active"), duration = c(0L, 
 0L, 0L, 0L, 0L, 0L, 0L, 60L, 0L, 0L, 0L, 0L, 0L, 0L, 56L, 0L, 
 0L, 0L, 0L, 0L, 37L, 0L, 0L, 0L, 0L, 0L, 60L, 0L)), .Names = 
 c("dialled", "Ringing", "state", "duration"), class = "data.frame", 
 row.names = c(NA, -28L))

newdata

 df <- structure(list(dialled = c(123L, 123L, 123L, 123L, 123L, 123L, 
 222L, 222L, 222L, 123L, 123L, 123L), Ringing = c(NA, NA, NA, 
 NA, NA, NA, NA, NA, NA, NA, NA, NA), state = c(NA, NA, NA, NA, 
 NA, NA, "inactive", "inactive", "inactive", "inactive", "inactive", 
 "active"), duration = c(0L, 0L, 60L, 0L, 0L, 70L, 0L, 0L, 37L, 
 0L, 0L, 60L)), .Names = c("dialled", "Ringing", "state", "duration"
 ), class = "data.frame", row.names = c(NA, -12L))