Bug in boxplot/mlab.prctile


> I noticed that the boxplot function incorrectly calculates the
> location of the median line in each box. As a simple example,
> plotting
> the dataset [1, 2, 3, 4] incorrectly plots the median line at 3.
I can confirm this.

> [..]
> I would suggest that mlab.prctile be fixed to conform to some one
> or other of these methods, rather than adding to the proliferation of
> approaches to quantile-calculation. Is there any motivation for
> always truncating to integer (other that "it's quicker to type" :-)?
And I agree here. I also recently (before I noticed this thread) posted a bug report #3151034 [1]

There is also documented, that the mlab.prctle function does not yield the same results as scipy.stats.scoreatpercentile. In addition to make the confusion complete matlab reports yet another result ... But I think at least matplotlib and the scipy-stats-package should agree.


[1] http://sourceforge.net/tracker/?func=detail&aid=3151034&group_id=80706&atid=560720


Jochen Deibele, PhD candidate, Dipl.-Ing.
Department of Circulation and Medical Imaging
Norwegian University of Science and Technology (NTNU)
Phone: +47 728 28028 E-Mail: jochen.deibele@...2639...