calculating time interval distributions
Your question seems rather poorly specified to me, and you may have to clarify it further, but I'll make a stab at it. IF one can assume that: 1. "a" must occur before "b", "b" before "c" etc. AND 2. "sec" is always increasing THEN z <- tapply(sec, ind, FUN = min) gives the first appearance sec value for each letter and outer(z,z,"-") gives the matrix of differences (in which the upper triangle is the negative of the lower) Is that what you wanted? -- Bert
On Wed, Nov 16, 2011 at 6:00 AM, Grant Gillis <grant.j.gillis at gmail.com> wrote:
Dear List,
I have data on a approximately 100 individuals visiting a a central logging
station over a 1000 times. ?I would like to be able to calculate the
distribution of inter-visit time intervals for all possible pairs am stuck
on how to code for this. ?Single pairs are not a problem but extending it
has been difficult for me. ?So for the toy data below I'd like to calculate
for each 'a' how long until I see 'b' as well as for each 'b', how long
until I see 'a' and so on for all possible pairs (2 triangle of a matrix?)
Thanks for any help, hints, and suggestions.
Grant
toy data:
ind <- ?c('a', 'b', 'a', 'c', 'b', 'b', 'c', 'a', 'c')
sec <- c(1, 3, 5, 6, 12, 22, 66, 85, 99)
What I am looking for
ab
2
? ? ? ?[[alternative HTML version deleted]]
______________________________________________ R-help at 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.
Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm