st: How to overlay multiple twoway bar graphs?

["McDermaid, Cameron" <Cameron.McDermaid@ottawa.ca>]

I want to graph duration of disease outbreaks against the date of occurrence by aetiological agent for multiple sites so each site will have its own summary graph.  I've been trying to generate bar graphs such that duration is on the y-axis, date of onset along the x-axis and each aetiological agent represented by it's own bar colour.

I can get the result I want by manually using || to overlay bar graphs where each additional plot represents the duration and onset date of a particular aetiological agent. 
e.g. 
twoway bar duration index_date if site==2 & aetiologicagent=1 || duration index_date if site==2 & aetiologicagent=4

However, I’d like to script this. I have 24 sites and not all sites had outbreaks with the same aetiological agents and, over time, the within-site agents may change depending on the time period. That’s a lot of recoding if I take a manual approach to write disease specific graphs.  What I’d like to do is essentially overlays the graphs generated by: 

.twoway bar duration index_date if site==2, by(aetiologicagent)

into one graph. I would loop through the instances of the sites to get summary graphs for each.   

I’ve tried a number of things without achieving the results I wanted. The only thing I haven’t tried is to generate binary dummy variables for each aetiologic agent and include them all in a graph statement as overlays using ||. I’d expect the instances of aetiological agents that don’t exist for that institution would not be plotted.

Any suggestions of alternative solutions?


- cam
--
Cameron McDermaid MHSc
Epidemiologist
Ottawa Public Health
100 Constellation Cr, Ottawa ON K2G 6J8
vox: 613-580-6744x15321
fax: 613-580-9601

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