Remove identical values if the same as previous in a time series

Question

I have a time series:

 df <- data.frame(t=1:10, x= c(5,7,8,9,5,5,5,5,4,3))

I want to remove values that are identical to the previous value to obtain:

 x = c(5,7,8,9,5,4,3)

I tried:

 df[unique(df$x),]

But this gives the incorrect answer.

Answer 1

You can do:

df[c(1, diff(df$x)) != 0, ] 

   t x
1  1 5
2  2 7
3  3 8
4  4 9
5  5 5
6  9 4
7 10 3

Answer 2

With dplyr, you can do:

df %>%
 filter(x != lag(x, default = first(x)-1))

   t x
1  1 5
2  2 7
3  3 8
4  4 9
5  5 5
6  9 4
7 10 3