Re: st: count (Stata 8)

[Heather Gold <heg2001@med.cornell.edu>]

Thanks for the replies thus far.
I'd prefer a scalar so I don't have to generate the extra variables with a 
value attached to each subject.

Based on all the comments you have generously offered, I'm closer to a 
solution:

forvalues i=1995/1998 {
        count if dxflag==1 & year==`i'
        scalar cases`i' = r(N)
        count if year==`i'
        scalar total`i' = r(N)
        scalar prev`i' = cases`i'/total`i'
}
The problem is this doesn't give me different denominators (ie, total for 
each year)...thoughts?
Heather


> -------Original Message-------
>
> > Dear Listers -
> >
> > I know this must be simple, but something eludes me.
> > I have a data set of subjects (cases and non-cases) by year and am trying 
> > to calculate a prevalence per year, ie, [cases/(cases+noncases)].
> > ie, data look like this:
> > id      year    dxflag
> > 1       1995    1
> > 1       1996    0
> > 1       1997    0
> > 2       1995    0
> > 2       1996    1
> > ...
> >
> > I found that I can write
> > by year: count if dxflag==1
> > or
> > by year: count
> >
> > and these return number of cases in the first line, and count of total 
> > population in the second line, just as I want.
> > But what I need are these values as scalars, so I can create a prevalence 
> > per year. In the Stata 8 help/manual it says that -count- saves the 
> > scalar of number of observations in r(N), but I can't seem to get this 
> > number to appear. Do I actually have to write a program to calculate 
> > this? And how does the "by year" part fit in...?
> >
> > Thanks for your help,
> > Heather
> >
> > *
> > *   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/
> --------End of Message--------
>
> There are 10 kinds of people in the world, those who know binary and those 
> who don't.
>
> *
> *   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/
:::::::::::::::::::::::::::::::::::::::::::::
Heather Taffet Gold, PhD
Assistant Professor
Department of Public Health
Weill Medical College of Cornell University
411 E. 69th Street
New York, New York 10021

E: heg2001@med.cornell.edu
P: (212) 746-1245
F: (212) 746-8544 

*
*   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/