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From |
"Martin Weiss" <martin.weiss1@gmx.de> |

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

Subject |
RE: st: Overriding a loop if 0 observations using tabstat |

Date |
Tue, 27 Apr 2010 20:29:13 +0200 |

<> Jeph, out of curiosity, what kind of equipment is it that throws up these numbers? Mine is 64 bit MP 4 on Windows 7 with 4G Ram. HTH Martin -----Original Message----- From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Jeph Herrin Sent: Dienstag, 27. April 2010 20:27 To: statalist@hsphsun2.harvard.edu Subject: Re: st: Overriding a loop if 0 observations using tabstat t=48.90; t=60.45; t=72.30. :> Martin Weiss wrote: > <> > > t=100.28; t=207.58; t=241.55. :-) > > > HTH > Martin > > > -----Original Message----- > From: owner-statalist@hsphsun2.harvard.edu > [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox > Sent: Dienstag, 27. April 2010 19:08 > To: statalist@hsphsun2.harvard.edu > Subject: RE: st: Overriding a loop if 0 observations using tabstat > > Good question. I decided to do some timings to support -- or rebut -- my > feeling that -count- which just counts should be faster than -summarize, > meanonly- which does other stuff too and in turn than -summarize- which does > other stuff too. But although that's the order the timings are closer than I > guessed. Still, doing anything the quickest way does no harm and may give > valuable speed-up for large problems. > > Here is one test script. Compare your experiences: > > clear > set obs 100000 > set seed 2803 > gen y = runiform() > set rmsg on > > qui forval i = 1/10000 { > count if y > 0.5 > } > > qui forval i = 1/10000 { > su y if y > 0.5, meanonly > } > > qui forval i = 1/10000 { > su y if y > 0.5 > } > > My timings were t=187.49; 254.49; 313.38, which no doubt shows up the > Mesolithic age of my machine. > > Nick > n.j.cox@durham.ac.uk > > Martin Weiss > > " As a small detail of efficiency, I would always recommend -count- rather > than -summarize- for the purpose here." > > My earlier code did use -count-... What makes this thing more efficient, > though? Both are built-in, so they probably enjoy a big advantage over > everybody else anyway. So I guess the reason for your preference is the fact > that -count- calculates fewer results than -su, mean-? > > Nick Cox > > A secondary theme here is that this kind of code gets very difficult to > read, which makes it difficult to maintain and debug. > > I note that the condition > > intab1 == 1 & admit_ic == 1 & btwg < . > > is common to all the -summarize- and -tabstat- commands. That being so, you > could get that out of the way like this > > preserve > keep if intab1 == 1 & admit_ic == 1 & btwg < . > <stuff> > restore > > Your -tabstat- options that are constant can be put in a little bag: > > local opts stat(n mean median p25 p75 min max) col(stat) f(%9.0g) notot > nosep > > Now <stuff> can be rewritten > > forv i = 0/5 { > foreach y in male singlet { > forv s = 0/1 { > di "myga==`i' & `y'==`s'" > qui su bwtg if myga==`i' & `y' > if r(N) != 0 { > tabstat bwtg if myga==`i', `opts' by(`y') > } > } > } > } > > Now it is easier to see what is going on. I added some cosmetic changes too, > which this horrible mailer may well reverse. > > One puzzle: Did you mean to add the condition "& `y'" to the -summarize-? It > means the same as > > & `y' != 0 > > -- which may or may not be what you want. > > As a small detail of efficiency, I would always recommend -count- rather > than -summarize- for the purpose here. > > Nick > n.j.cox@durham.ac.uk > > sara khan > > Many thanks Maarten for your advice. I managed to resolve it with the > following code: > > forv i=0/5 { > foreach y in male singlet{ > forv s=0/1{ > di "myga==`i' & `y'==`s'" > qui su bwtg if myga==`i' & intab1==1 & admit_ic==1 & bwtg<. & `y' > if r(N)!=0{ > tabstat bwtg if myga==`i' & intab1==1 & admit_ic==1 & bwtg<., stat(n > mean median p25 p75 min max ) by(`y') col(stat) f(%9.0g) notot nosep > > } > } > } > } > > > On Tue, Apr 27, 2010 at 12:56 PM, Maarten buis <maartenbuis@yahoo.co.uk> > wrote: >> --- On Tue, 27/4/10, sara khan wrote: >>> I just tried this but the output only shows the display >>> results and nothing from tabstat. >> <snip> >> >> -capture- works for me: >> >> *----------------- begin example --------------------- >> sysuse auto, clear >> forvalues i = 0/5 { >> capture noisily tabstat mpg if rep78== `i', /// >> s(n mean) by(foreign) >> } >> *-------------------- end example ------------------- >> >> In order to debug your loop I would build it step by step: >> step 1: no looping, no locals, no -if- just a single -tatstat- command >> step 2: add -capture noisily- >> step 3: add some -if- conditions >> step 4: build a single loop (e.g. over i but not over y) >> etc. etc. > > * > * 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/ > > > * > * 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/ > * * 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/ * * 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: Overriding a loop if 0 observations using tabstat***From:*Jeph Herrin <junk@spandrel.net>

**References**:**Re: st: Overriding a loop if 0 observations using tabstat***From:*sara khan <sarakhanum84@googlemail.com>

**Re: st: Overriding a loop if 0 observations using tabstat***From:*Maarten buis <maartenbuis@yahoo.co.uk>

**Re: st: Overriding a loop if 0 observations using tabstat***From:*sara khan <sarakhanum84@googlemail.com>

**RE: st: Overriding a loop if 0 observations using tabstat***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**AW: st: Overriding a loop if 0 observations using tabstat***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**RE: st: Overriding a loop if 0 observations using tabstat***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**RE: st: Overriding a loop if 0 observations using tabstat***From:*"Martin Weiss" <martin.weiss1@gmx.de>

**Re: st: Overriding a loop if 0 observations using tabstat***From:*Jeph Herrin <junk@spandrel.net>

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