st: Stacked histogram - empty bins

[Allen Cheng <acscheng@gmail.com>]

I am trying to make a stacked histogram to show an epidemic in different
states by epidemiological week. I found Nick Cox's helpful instructions in 2006
using the undocumented command twoway__histogram_gen

The problem is that some weeks, some states do not have any cases, and this
makes a mess of trying to line up where rbar starts and ends. Is there any
way to "force" zeros into the weeks with no cases?

The commands I have tried are

twoway__histogram_gen admissiondate if state=="VIC", gen(freq_vic x_vic)
start (`startdate') width(7) freq
twoway__histogram_gen admissiondate if state=="ACT", gen(freq_act x_act)
start (`startdate') width(7) freq
twoway__histogram_gen admissiondate if state=="WA", gen(freq_wa x_wa) start
(`startdate') width(7) freq
gen freq1=freq_vic+freq_act
gen freq2=freq_vic+freq_act+freq_wa
tw (bar freq_vic x_vic if freq1<., ylab(r(0 .))) (rbar freq_vic freq1
x_act if freq1<.)
(rbar freq1 freq2 x_wa if freq2<.), xtitle(date) ytitle(number of cases)

Thanks
Allen Cheng
*
*   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/