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From |
"Jann Ben" <ben.jann@soz.gess.ethz.ch> |

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

Subject |
st: RE: Y axis values for hist ,density |

Date |
Thu, 27 Oct 2005 15:12:13 +0200 |

Bang! I don't agree. The purpose of a histogram is to make visible the shape of a density. It is therefore natural to report the y-axis in terms of a density. ben > -----Original Message----- > From: owner-statalist@hsphsun2.harvard.edu > [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of > Allan Reese (Cefas) > Sent: Thursday, October 27, 2005 3:03 PM > To: statalist@hsphsun2.harvard.edu > Subject: st: Y axis values for hist ,density > > > The default "hist x" command in Stata gives a Y axis labelled > a density. I've never given it much attention until I saw > the scale went up to 2 on a plot. Hold on, density functions > sum to 1 over the variable. > > Further investigation and discussion with Statacorp > identified that the default tries to make the "area" of the > bars add up to 1. If the number of bars changes, so does > their width and so does the Y labelling. In my example, the > data were discrete, so increasing the number of intervals did > not change the plot except to add more zero-height columns > and hence make each column narrower. > > hist x, bin(n) therefore caused different Y > labelling with varying n > hist x, xcale(xrange(0 n) did not affect the labelling, > though the bars got narrower with bigger n > hist x, frac and > hist x, discrete both gave correct labelling, and > the sum of column heights was 1. > > Do other users think this is perverse behaviour, especially > as the default? My take is that, when drawing a histogram, > the column width is taken as an arbitrary unit, not directly > related to the x-scale. The implication is that you need to > scale the height only when there are mixed-width columns, but > would not label the Y axis in "freq/absolute-width" units. > Having "densities" that vary and are in such peculiar units > (1/locust in my example!) does not seem helpful. > > Shoot me down > Allan > > > ************************************************************** > ********************* > This email and any attachments are intended for the named > recipient only. Its unauthorised use, distribution, > disclosure, storage or copying is not permitted. If you have > received it in error, please destroy all copies and notify > the sender. In messages of a non-business nature, the views > and opinions expressed are the author's own and do not > necessarily reflect those of the organisation from which it > is sent. All emails may be subject to monitoring. > ************************************************************** > ********************* > > > * > * 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/

**Follow-Ups**:**Re: st: RE: Y axis values for hist ,density***From:*Marcello Pagano <pagano@hsph.harvard.edu>

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