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From |
<cthompson@dfpm.utah.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: RE: Re: return list and by |

Date |
Tue, 13 Apr 2004 10:14:26 -0600 |

Many Thanks to both Nick Cox & Michael Blasnik for their suggestions! On 13 Apr 2004 at 10:43, Nick Cox wrote: > To expand on a few points: > > 1. The -egen- route is naturally fine whenever it > offers the statistic you want to keep. Note that > when you go > > by person : egen mean = mean(whatever) > > That mean will be repeated for every observation > for each person. For many purposes you will want > to use each mean just once. Tagging is one way to > do that > > egen tag = tag(person) > > tags just one observation for each person. Then > you can follow up with > > ... if tag > > If you look inside the -mean()- function you > will see that it does not use -summarize-. > > 2. -statsby- is what I call a reduction command. > You will get one observation for each person, in your > problem, i.e. you will lose the existing dataset. > Roger Newson's set of commands is another > example of a reduction approach. > > 3. Doing it yourself with a loop is not too > difficult, but you must loop over groups at > a minimum. One FAQ which may be of help is > http://www.stata.com/support/faqs/data/foreach.html > > Persons will have integer or string identifiers, > so using -levels- is often effective. Taking > your program > > > program mean_get > > syntax [varlist] > > foreach i of local varlist { > > generate overall2 = 0 > > by name, sort: summarize `i', meanonly > > local 1 = r(mean) > > by name, sort: replace overall2 = `1' > > } > > end > > let's forget that -egen- exists and write a program > that puts means of a varlist into variables -mean_*- > for a division by some required variable. > > program mean_get > * NJC after Clint Thompson 13 April 2004 > version 8 > syntax varlist(numeric), by(varname) > > // check new names will be OK > foreach v of local varlist { > confirm new var mean_`v' > } > > // this will fail if `by' is not categorical > qui levels `by', local(B) > capture confirm numeric var `by' > local isstr = _rc != 0 > > qui foreach v of local varlist { > gen mean_`v' = . > if `isstr' { > foreach b of local B { > su `v' if `by' == `"`b'"', meanonly > replace mean_`v' = r(mean) if `by' == `"`b'"' > } > } > else { > foreach b of local B { > su `v' if `by' == `b', meanonly > replace mean_`v' = r(mean) if `by' == `b' > } > } > } > end > > I added a bit more checking. There is still much that > could be added e.g. support for -if- and -in-. > > Nick > n.j.cox@durham.ac.uk > > Michael Blasnik > > > most directly: > > > > by name: egen overall2=mean(`i') > > > > will put the mean of var `i', calculated for each value of name, in > > overall2. Of course, this value will still be overwritten by the next > > var in the varlist if your loop is left as shown. > > > > More specifically, when you use constructs such as -by x: > > summ y- , you > > can't get at the individual results -- it's quite frustrating > > when you first > > discover this. Instead you either have to write your own loop across > > groups, or else you may be able to use an -egen- function or -statsby- > > (or perhaps -parmby-). > > cthompson@dfpm.utah.edu > > > > Is there a way to save the mean in r() for each value of a > > > variable? More specifically, I want the mean for each > > > different person contained within the variable 'name'. My > > > programming experience in Stata is quite limited so I'd > > > appreciate any advice; the shrapnel from my attempt at coding > > > is pasted below: > > > > > > program mean_get > > > syntax [varlist] > > > foreach i of local varlist { > > > generate overall2 = 0 > > > by name, sort: summarize `i', meanonly > > > local 1 = r(mean) > > > by name, sort: replace overall2 = `1' > > > } > > > end > > > > > > When I run this, it returns the mean from the last value in > > > 'name' and uses it to replace all values of 'overall2'. Any > > > suggestions? > > * > * 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**:**st: RE: Re: return list and by***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

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