From: Anupam Tyagi <AnupTyagi_at_yahoo.com>

Date: Tue 19 Sep 2006 - 06:51:51 GMT

R-help@stat.math.ethz.ch 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. Received on Tue Sep 19 18:28:26 2006

Date: Tue 19 Sep 2006 - 06:51:51 GMT

Greg Snow <Greg.Snow <at> intermountainmail.org> writes:

*>
*

> You may want to rethink your whole approach here:

*>
**> 1. Pie charts are usually a poor choice of graph, there are better
**> choices.
**> 2. Adding percentages to a pie chart is a way of admitting that the pie
**> chart is not doing the job.
**> 3. If you want people to compare percentages, then a table is what is
**> needed.
**> 4. A pie chart with percentages added is essentially a colorful but
**> poorly layed out table.
**>
**> Consider using a dotplot instead of a pie chart, it changes the job of
**> the viewer from comparing areas/angles (done poorly by humans) to
**> comparing positions along a common scale (done well by humans).
*

I think dot charts (plots) are very useful, but they are not substitutes for a pie chart: they do not show a comparison between the total and the individual value; have a different scale (linear, usually), and are visually not suitable to answer some questions that a pie chart can answer (is the value approximately less than a fourth of the total? Is it less than half?). For some of these questions, even dot-charts require a value label, or the user doing mental calculations to guess approximations.

I think I am quite attuned to getting approximate fractions from a pie-chart in shorter time, than on a linear scale like the dot-chart.

A modification in a pie chart that draws overlapping areas with a common start
point at the top of the circle, can make is more informative than a dot-chart.
Something like:

* Start drawing at the top of the circle, as zero (degree/area).
* Draw the representation of every value starting from the top, as zero,
representing it as a labled line from the center of the circle to the boundary
(can use colors where possible).

* Use two lables for the circular axis, inside one for percentages, outside for
values.

What is the simplest way to draw this in R?

Anupam.

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