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From |
Keith Dear <keithdear4@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: qplot , over() |

Date |
Sat, 24 Mar 2012 09:17:00 +1100 |

Thanks Nick, the new version does what I wanted. In passing -- while I agree it's not hard to DIY this, in fact this is a nice example of why it's better to use a provided (authorised) program when possible. Instead of your careful code, I would have written: . bys mpg (foreign): gen pp=(_n-0.5)/_N It took me some thought to see why you didn't do it that way (they give exactly the same result for the auto data). Keith On 23 March 2012 23:53, Nick Cox <njcoxstata@gmail.com> wrote: > By the way, a do-it-yourself approach is easier than might be thought > > sysuse auto, clear > egen rank = rank(mpg), unique by(foreign) > egen n = count(mpg), by(foreign) > gen pp = (rank - 0.5 ) / n > separate mpg, by(foreign) veryshortlabel > scatter mpg? pp > > SJ-7-2 gr0027 . . Stata tip 47: Quantile-quantile plots without programming > . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox > Q2/07 SJ 7(2):275--279 (no commands) > tip on producing various quantile-quantile (Q-Q) plots > > Note that this recipe is strong enough to cope with ties and missing > values and flexible in that you can insert your own definition of > plotting positions (-pp- above) if you don't like (i - 0.5) / n for > some reason. > > Nick > > On Fri, Mar 23, 2012 at 12:36 PM, Nick Cox <njcoxstata@gmail.com> wrote: >> In revising -qplot- for SJ 10-4 I inadvertently introduced a bug in >> implementation of the -over()- option. I thought no one had noticed >> but me, but Keith has been bitten by it. >> >> The bug has already been fixed in a update due shortly in SJ 12-1. I >> will send Keith a copy of the revised files. >> >> Nick >> >> On Fri, Mar 23, 2012 at 12:22 PM, Keith Dear <keithdear4@gmail.com> wrote: >> >>> How can I get several quantile plots in one diagram? >>> (There have been past threads on this, but I found no mention of what >>> I am getting.) >>> >>> sysuse auto >>> replace mpg=mpg/2 if foreign // for greater separation >>> qplot mpg, by(foreign) // two distinct curves, which I would like >>> to plot together >>> qplot mpg, over(foreign) // points on a single curve, not what I expected >>> >>> Am I misunderstanding the help file? It seems to imply that by() and >>> over() give the same set of curves, which is what I want but isn't >>> what happens: >>> >>> ---- help qplot >>> by(varname[, suboptions]) specifies that calculations be carried out >>> separately for each distinct value of a >>> specified single variable. Results will be shown separately in >>> distinct panels. See [G] by_option. >>> over(varname) specifies that calculations be carried out separately >>> for each distinct value of a specified >>> single variable. Curves will be shown together within the >>> same panel. over() is only allowed with a single >>> varname. >>> ---- >>> >>> -qplot- is by NJC out of -net install gr42_5.pkg- > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ -- Dr Keith Dear National Centre for Epidemiology and Population Health ANU College of Medicine, Biology and Environment Australian National University Canberra, ACT 0200 Australia Phone +61 (02) 6273 2208 * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: qplot , over()***From:*Nick Cox <njcoxstata@gmail.com>

**References**:**st: qplot , over()***From:*Keith Dear <keithdear4@gmail.com>

**Re: st: qplot , over()***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: qplot , over()***From:*Nick Cox <njcoxstata@gmail.com>

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