Hi,
I am somewhat disturbed by the new 3D pie-charts (and the possibility of
further 3D charts).
Unfortunately, 3D charts DO NOT add any statistical benefits and should
be strongly discouraged!!! This view is held by many renowed
statisticians, including the late Prof. Alvin Feinstein. I have
*briefly* discussed this issue on
http://wiki.services.openoffice.org/wiki/Statistical_Data_Analysis_Tool
, and I hope to have more time to expand it even further (see also
Feinstein AR. Principles of Medical Statistics. Chapman & Hall 2002)
The basic feature of 3D pies is to represent accurately the magnitude of
the variable. The *AREA* of the pie is directly proportional with the
variable of interest (and so it is proportional with the outer length).
In a 3D pie, everything is distorted (to create the 3D-effect), so the
area, the outer length, and the perception of these values is NO LONGER
CORRECT!!!
There is NO NEED for a 3rd dimension in pie charts (it simply does NOT
bring further information). Therefore, the user should be WARNED, IF
selecting a 3D chart, that this is statistically wrong and unnecessary.
I hope that no further precious time is wasted on 3D charts.
*There are however some aspects that NEED IMPROVEMENT!!!*
One significant problem of the pie chart is when having very small values:
- consider: 40%, 30%, 25%, 2%, 1.3%, 1%, 0.7%;
- the problem is, the last 4 values are pretty small and CANNOT be
easily represented on a pie-chart!!!
This problem should be somehow solved. I have some ideas, but non is
universal. Actually, there simply ISN' T a universally applicable solution.
e.g.: - Chart should warn the user that the 4 values are very small and
should possibly be merged into one value
- alternatively: create an insert having only the 4 values magnified
- some other alternatives
Another feature is discussed in issue 366 (Select range for errorbars,
http://qa.openoffice.org/issues/show_bug.cgi?id=366). I have also added
a (two) potentially relevant comment(s) (close to the end of the
thread). Please read it, too.
If there are any further questions, I would be glad to help. (Please
leave me however some time to respond; I am currently quite under stress
and also work on a 2nd wiki,
http://wiki.services.openoffice.org/wiki/Bib-Keywords).
Kind regards,
Leonard Mada
[aka discoleo]
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