hello, i have been using ccf() to look at the correlation between lightning and electrogamnetic data. for the most part it has worked exactly as expected. however, i have come across something that puzzles me a bit:
> x <- c(1, 0, 1, 0, 1, 0) > y <- c(0, 0, 0, 0, 0, 0) > ccf(x, x, plot = FALSE) Autocorrelations of series 'X', by lag -4 -3 -2 -1 0 1 2 3 4 0.333 -0.500 0.667 -0.833 1.000 -0.833 0.667 -0.500 0.333 > ccf(x, y, plot = FALSE) Autocorrelations of series 'X', by lag -4 -3 -2 -1 0 1 2 3 4 NaN NaN NaN NaN NaN NaN NaN NaN NaN > y <- c(1, 1, 1, 1, 1, 1) > ccf(x, y, plot = FALSE) Autocorrelations of series 'X', by lag -4 -3 -2 -1 0 1 2 3 4 NaN NaN NaN NaN NaN NaN NaN NaN NaN i don't see why the result from ccf() would be NaN if the elements of y are all the same... perhaps i am just being silly or missing something. but if i work this out by hand, then i get a proper result. so, why not with ccf()? thanks for the help! best regards, andrew. -- Andrew B. Collier Space Physics Group Hermanus Magnetic Observatory Antarctic Research Fellow tel: +27 31 2601157 Space Physics Research Institute fax: +27 31 2616550 University of KwaZulu-Natal, Durban, 4041, South Africa gsm: +27 83 3813655 ______________________________________________ R-help@stat.math.ethz.ch 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.