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Re: st: detonator plot with three grouping variables


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: detonator plot with three grouping variables
Date   Thu, 9 May 2013 11:49:03 +0100

I agree strongly with David.

I think I heard the term "detonator plots" from Stata user and
Statalist member Paul Seed at a users' meeting several years ago. He
may care to comment on whether it's his coinage.

Independently of that, and echoing David, it's my impression that the
term "dynamite plot" is more common.

Naturally what you call the beast is not central here, but it is
germane in so far as searching for "dynamite plot" on the internet
yields good discussions such as

http://biostat.mc.vanderbilt.edu/twiki/pub/Main/TatsukiRcode/Poster3.pdf

The key issues are (to me)

1. Such plots omit detail which you should care about showing (when
it's your data) or examining (always).

2. The visual signal strongly emphasises mean values relative to zero,
by the solid or thick bars, and plays down uncertainty, shown by the
intervals. Comparison with zero can be an important comparison, but
it's often not of scientific interest or concern.

A much more informative display is available through (e.g.)
-stripplot- (SSC) which allows error bars to be shown with raw data.

In terms of what Ronnie wants to do in Stata, his question is
puzzling, because the UCLA FAQ he cites explains in detail that -graph
bar- is a dead end here and you must switch to -twoway bar-.

Nick
njcoxstata@gmail.com

On 9 May 2013 04:47, David Hoaglin <dchoaglin@gmail.com> wrote:
> Ronnie,
>
> A good first step would be to omit the bars entirely.  Freeman et al.
> (2008) discuss that type of plot under the name "dynamite plunger
> plot" in their chapter "How to display data badly."  The bars take up
> space to no good purpose.  A more effective plot would show the
> estimates with error bars or confidence intervals (and an explanation
> of whether the intervals are error bars or confidence intervals).
>
> David Hoaglin
>
> Freeman JV, Walters SJ, Campbell MJ (2008). How to Display Data.  BMJ Books.
>
> On Wed, May 8, 2013 at 5:49 PM, Ronnie Babigumira <rb.glists@gmail.com> wrote:

>> I am trying to create a detonator plot like the one in this example http://www.ats.ucla.edu/stat/stata/faq/barcap.htm only I have 3 levels. Here is an example using the accessible auto data
>>
>> sysuse auto,clear
>> egen lwst = fill(1,2,1,2)
>> recode rep78 (1 2 = 3)
>>
>> What I would like to do is add error bars to this plot
>>
>> gr bar price, over(lwst) over(foreign) over(rep78)
>>
>> Any help is much appreciated
>>
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