Hi:

This recent thread revealed that a package on R-forge for calculating earth
movers distance is available:

http://r.789695.n4.nabble.com/Measure-Difference-Between-Two-Distributions-td2712281.html#a2713505

HTH,
Dennis

On Tue, Oct 12, 2010 at 7:39 PM, Michael Bedward
<michael.bedward@gmail.com>wrote:

> 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.Snow@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.snow@imail.org
> > 801.408.8111
> >
> >
> >> -----Original Message-----
> >> From: r-help-bounces@r-project.org [mailto:r-help-bounces@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.
>

	[[alternative HTML version deleted]]

