Collapsing a vector/data-frame based on the previous values
Here is another way of doing it:
states <- structure(list(Date = c("24/07/2012", "25/07/2012", "26/07/2012",
+ "27/07/2012", "28/07/2012", "24/07/2012", "25/07/2012", "26/07/2012",
+ "27/07/2012", "28/07/2012"), State = c(1L, 1L, 1L, 1L, 1L, -1L,
+ -1L, -1L, 1L, -1L)), .Names = c("Date", "State"), class = "data.frame",
+ row.names = c(NA,
+ -10L))
# mark the state changes states$diff <- c(TRUE, diff(states$State) != 0) states[states$diff,]
Date State diff 1 24/07/2012 1 TRUE 6 24/07/2012 -1 TRUE 9 27/07/2012 1 TRUE 10 28/07/2012 -1 TRUE On Tue, Jul 24, 2012 at 2:40 AM, Raghuraman Ramachandran
<optionsraghu at gmail.com> wrote:
Hello
I have a data frame like this:
dput(states)
structure(list(Date = c("24/07/2012", "25/07/2012", "26/07/2012",
"27/07/2012", "28/07/2012", "24/07/2012", "25/07/2012", "26/07/2012",
"27/07/2012", "28/07/2012"), State = c(1L, 1L, 1L, 1L, 1L, -1L,
-1L, -1L, 1L, -1L)), .Names = c("Date", "State"), class = "data.frame",
row.names = c(NA,
-10L))
State
Date State
1 24/07/2012 1
2 25/07/2012 1
3 26/07/2012 1
4 27/07/2012 1
5 28/07/2012 1
6 24/07/2012 -1
7 25/07/2012 -1
8 26/07/2012 -1
9 27/07/2012 1
10 28/07/2012 -1
I wish to collapse it into a smaller one based on the state value. If state
is 1 already then the second state (and the row) is to be removed till a
new state is found and so on.. States can be 1 or -1 only. So in the
previous example the new data frame should be:
Date State 24/07/2012 1 24/07/2012 -1 27/07/2012 1 28/07/2012 -1 Can
someone help?
Thx
Raghu
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