aledanda wrote:
Hi,
I need your help.
I have a vector of numbers reflecting the switch in the perception of a
figure. For a certain period I have positive numbers (which reflect the
perception A) then the perception changes and I have negative numbers
(perception B), and so on for 40000 iterations. I need to take the rate of
this switch for my analysis. Namely, I need a new vector with numbers which
reflect how many digit follows in sequence before the change in perception
(and then I have to take the reciprocal of these numbers in order to obtain
the rate but is not a problem). For example, suppose that the new vector
looks like this: new <- c(5,7,8,9) , 5 numbers positive then the perception
changes and 7 negative numbers follow, then it changes again and 8 positive
follows and so on..
In brief I need to write a little script that detects the change in sign of
the elements of the vector and count how many positive and how many negative
digits there are in sequence.
I would use the for loop, I started but then i don't know how to continue
rate <- vector()
for(i in (length(a)) rate <- (a[i]> 0 ????
..can you help me?
See ?sign and ?rle which together yield:
a <- c(-1, -2, -3, 1, 2, -1)
rle(sign(a))
#Run Length Encoding
# lengths: int [1:3] 3 2 1
# values : num [1:3] -1 1 -1
## or just the vector you want is:
rle(sign(a))$lengths
[1] 3 2 1
Uwe Ligges
Alessandra
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
