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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
RE: st: RE: broken axis symbol? |

Date |
Wed, 14 May 2003 21:15:29 +0100 |

Nick n.j.cox@durham.ac.uk > -----Original Message----- > From: owner-statalist@hsphsun2.harvard.edu > [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Nick Cox > Sent: 14 May 2003 19:39 > To: statalist@hsphsun2.harvard.edu > Subject: RE: st: RE: broken axis symbol? > > > Constantine Daskalakis > > > > At 01:04 PM 5/14/03, Nick Cox wrote: > > >As I recall, Darrell Huff in his 1954 book implied that axes > > >which don't start at zero are deceitful. And I seem > > >to remember my high-school science teachers saying the > > >same thing in the 1960s and recommending a scale break. > > >[snip] > > > > > > > I beg to differ on this one Nick. > > I think being able to "break" the axis is a crucial feature > > in plots. > > > > Suppose I want to plot the percent of adolescents who've > > ever used a > > computer in the US over the past 10 years (estimated from > repeated > > cross-sectional samples). During that period, this > > proportion has gone up > > from about 70% or so to over 95%. > > > > Y-axis is "% used computer" and X-axis is calendar time (years). > > > > First, I don't want to plot on the log scale. Why would I? > > > > Second, I don't want to waste three quarters of my graph > > area by using the > > full scale of the Y axis (i.e., 0-100%), when all my > > measurements are > > around 85-95%. > > > > I can start my Y-axis at, say, 60%, but I think that's more > > misleading than > > starting at 0% and having a "break" to jump to, say, 60%. > > Your example doesn't convince me, but I think there > are better ones. In principle, I agree with this: > there is sometimes a need for scale breaks. > > Evidently I should make my position clearer. > > Ernest asked for a scale break indicated > in a particular way by a zig-zag on the axis. > > My assertion is that not using that is not bad > practice, contrary to some old advice, and to > your apparent position here. > > My question is how far it is really used in > scientific literature(s). > > In addition, I drew attention to Cleveland's > suggestion for a full scale break whenever > a scale break is deemed essential. > Graphically this is a very different > practice. It is a matter of dividing the > data region into different panels. > > In fact, one objection to the zaggy > axis is that it is not nearly drastic > enough as a way of signalling something > fundamental about the graph. Users too naive > or lazy to look at labels are also likely > to overlook the zags (or perhaps the zigs). > > In my previous posting > I referred to an FAQ I wrote giving > a real example and explaining one way to > do it in Stata <8, at least roughly, > and as said the principle could be > applied with Stata 8. > > What would do you do with a graph showing > SARS cases against time? Time starts > late 2002, say. > > Nick > n.j.cox@durham.ac.uk > > * > * For searches and help try: > * http://www.stata.com/support/faqs/res/findit.html > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**RE: st: RE: broken axis symbol?***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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