Re: st: RE: Cumulative Frequencies within Groups

[Nick Cox <njcoxstata@gmail.com>]

See also -groups- (SJ and SSC).

Nick


On 3 Aug 2012, at 22:20, "Ben Hoen" <bhoen@lbl.gov> wrote:

> As often happens...preparing the email prompted me to think  
> differently.
>
> Here is the solution:
>
> *=========== Begin ==================
>
> sysuse auto, clear
> g levels=(int(4*runiform()))+1 //to create an categorical variable
> representing 4 groups
> bys levels rep78 : gen freq = _N
> bys levels rep78 : gen cumfreq = _N if _n == 1
> bys levels: replace cumfreq = sum(cumfreq)
> bys levels: tabdisp rep78, cell(freq cumfreq)
>
> *============ End ====================
>
> Ben Hoen
> LBNL
> Office: 845-758-1896
> Cell: 718-812-7589
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Ben Hoen
> Sent: Friday, August 03, 2012 4:49 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Cumulative Frequencies within Groups
>
> Hi all,
>
> I have been unable to figure out how to create cumulative  
> frequencies within
> groups.
>
> This Nick Cox entry provided a great description for how to create
> cumulative frequencies for a whole set of data:
> http://www.stata.com/support/faqs/data-management/tabulating-cumulative-freq
> uencies/
>
> But I have not been able to apply the same logic to groups within my
> dataset.
>
> For the full dataset this code works perfectly (as Nick provided)
>
> *======= Begin ===============
>
> sysuse auto, clear
> by rep78, sort: gen freq = _N
> by rep78: gen cumfreq = _N if _n == 1
> replace cumfreq = sum(cumfreq)
> tabdisp rep78, cell(freq cumfreq)
>
> * ========== End ==================
>
> I would like to apply the same logic to groups of cases.  Here is my  
> best
> attempt.
>
> * =========== Begin ===============
>
> g levels=(int(4*runiform()))+1 //to create an categorical variable
> representing 4 groups
>
> su levels, meanonly
>
> forvalues i = 1/`r(max)' { //max is used because often I will not  
> know the
> number of groups
> bys rep78: gen freqtemp=_N if levels==`i'
> by rep78: gen cumfreqtemp=_N if _n==1 & levels==`i'
> replace cumfreqtemp=sum(cumfreqtemp) if levels==`i'
> replace freq=freqtemp if levels==`i'
> replace cumfreq=cumfreqtemp if levels==`i'
> drop freqtemp cumfreqtemp
>
> }
> *
>
> bys levels: tabdisp rep78, cell(freq cumfreq)
>
> * =========== End =====================
>
> As one can see, my code has a problem that I cannot discern.
>
> Any ideas?
>
> Thanks, in advance,
>
> Ben
>
>
> Ben Hoen
> Principal Research Associate
> Lawrence Berkeley National Laboratory
> Office: 845-758-1896
> Cell: 718-812-7589
> bhoen@lbl.gov
> http://eetd.lbl.gov/ea/emp/staff/hoen.html
>
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