Just to add to Greg's comments: I've previously used 'Earth Movers Distance' to compare histograms. Note, this is a distance metric rather than a parametric statistic (ie. not a test) but it at least provides a consistent way of quantifying similarity.
It's relatively easy to implement the metric in R (formulating it as a linear programming problem). Happy to dig out the code if needed. Michael On 13 October 2010 02:44, Greg Snow <greg.s...@imail.org> wrote: > That depends a lot on what you mean by the histograms being equivalent. > > You could just plot them and compare visually. It may be easier to compare > them if you plot density estimates rather than histograms. Even better would > be to do a qqplot comparing the 2 sets of data rather than the histograms. > > If you want a formal test then the ks.test function can compare 2 datasets. > Note that the null hypothesis is that they come from the same distribution, a > significant result means that they are likely different (but the difference > may not be of practical importance), but a non-significant test could mean > they are the same, or that you just do not have enough power to find the > difference (or the difference is hard for the ks test to see). You could > also use a chi-squared test to compare this way. > > Another approach would be to use the vis.test function from the TeachingDemos > package. Write a small function that will either plot your 2 histograms > (density plots), or permute the data between the 2 groups and plot the > equivalent histograms. The vis.test function then presents you with an array > of plots, one of which is the original data and the rest based on > permutations. If there is a clear meaningful difference in the groups you > will be able to spot the plot that does not match the rest, otherwise it will > just be guessing (might be best to have a fresh set of eyes that have not > seen the data before see if they can pick out the real plot). > > -- > Gregory (Greg) L. Snow Ph.D. > Statistical Data Center > Intermountain Healthcare > greg.s...@imail.org > 801.408.8111 > > >> -----Original Message----- >> From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- >> project.org] On Behalf Of solafah bh >> Sent: Monday, October 11, 2010 4:02 PM >> To: R help mailing list >> Subject: [R] compare histograms >> >> Hello >> How to compare two statistical histograms? How i can know if these >> histograms are equivalent or not?? >> >> Regards >> >> >> >> [[alternative HTML version deleted]] > > ______________________________________________ > 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. > ______________________________________________ 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.
