On Aug 20, 2010, at 9:19 AM, Izidine Pinto wrote:
Dear R users I am using KS test to compare two different distribution for the same variable (temperature) for two different time periods. H0: the two distributions are equal H1: the two distributions are different ks.test (temp12, temp22) Two-sample Kolmogorov-Smirnov test data: temp12 and temp22 D = 0.2047, p-value < 2.2e-16 alternative hypothesis: two-sided Warning message: In ks.test(temp12, temp22) : cannot compute correct p-values with ties
This question comes up so often there should probably be a FAQ, but I just checked and there is not one (yet).
It's only a warning, but it does mean that you need to check the distribution of your values to see how far they depart fro the theoretical ideal of continuous functions for which the KS test was developed. There are alternatives to the ordinary KS test from wilcox.test and the help page refers you to wilcox_test in package coin with a note that it handles situations with ties.
(With a p-value that is numerically equivalent to zero, it seems unlikely that the final answer will be materially different than what you are now looking at.)
-- David
I don't rally know how to interpret the output from R. Any help is appreciated.
-- David Winsemius, MD West Hartford, CT ______________________________________________ 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.
