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Re: st: detonator plot with three grouping variables
From
"Roger B. Newson" <[email protected]>
To
[email protected]
Subject
Re: st: detonator plot with three grouping variables
Date
Thu, 09 May 2013 12:05:27 +0100
My take on detonator plots is that they CAN be useful, and complementary
to the CI plots for differences, because an audience presented with mean
or prevalence differences will frequently ask what these differences are
differences between. The important thing (I find) is to make both
confidence limits visible, which of course makes the bars look a little
bit less like detonators. People commonly make the mistake of coloring
the bars black, and leaving the comfidence limits black too, which makes
the bars look a bit more like detonators. I usually color the bars
white, or light shades of grey.
The -eclplot- package, downloadable from SSC, is my usual tool for
making detonator plots, specified by the options
eplottype(bar) rplottype(spike)
or
eplottype(bar) rplottype(cap)
depending on whether or not I want the confidence limits to have caps.
And I usually use my graphics scheme -scheme_rbn1mono-, which you can
also download from SSC, and which usually colors bars white, or fairly
light shades of gray, unless instructed to do otherwise. And -eclplot-
will usually put the confidence limits in the foreground, and the bars
in the background, unless instructed otherwise.
I hope this helps.
Best wishes
Roger
Roger B Newson BSc MSc DPhil
Lecturer in Medical Statistics
Respiratory Epidemiology and Public Health Group
National Heart and Lung Institute
Imperial College London
Royal Brompton Campus
Room 33, Emmanuel Kaye Building
1B Manresa Road
London SW3 6LR
UNITED KINGDOM
Tel: +44 (0)20 7352 8121 ext 3381
Fax: +44 (0)20 7351 8322
Email: [email protected]
Web page: http://www.imperial.ac.uk/nhli/r.newson/
Departmental Web page:
http://www1.imperial.ac.uk/medicine/about/divisions/nhli/respiration/popgenetics/reph/
Opinions expressed are those of the author, not of the institution.
On 09/05/2013 11:49, Nick Cox wrote:
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
[email protected]
On 9 May 2013 04:47, David Hoaglin <[email protected]> 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 <[email protected]> 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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