Remove consecutive duplicate entries

Question

How to remove consecutive duplicate entries in R? I think with may be used but can't think how to use it. Illustrating one example:

read.table(text = "
   a        t1
   b        t2
   b        t3
   b        t4
   c        t5
   c        t6
   b        t7
   d        t8")

Sample Data: D

    events    time
       a        t1
       b        t2
       b        t3
       b        t4
       c        t5
       c        t6
       b        t7
       d        t8

Required Outcome:

     events     time
       a        t1
       b        t4
       c        t6
       b        t7
       d        t8

`

Answer 1

Yet an other one, assuming your data.frmae is named d:

d[cumsum(rle(as.numeric(d[,1]))$lengths),]
  V1 V2
1  a t1
4  b t4
6  c t6
7  b t7
8  d t8

Answer 2

EDIT: Not exactly correct as it only shows one b row. You can also use the duplicated() function

x <- read.table(text = "    events    time
   a        t1
   b        t2
   b        t3
   b        t4
   c        t5
   c        t6
   d        t7", header = TRUE)
#Making sure the data is correctly ordered!
x <- x[order(x[,1], x[,2]), ]      
x[!duplicated(x[,1], fromLast=TRUE), ]