Re: st: Three-way (or more) histograms in Stata

[William Buchanan <william@williambuchanan.net>]

Hi Tim,

Did you consider -kdensity-? You can overlay multiple plots using -tw- with it as well.

HTH,
Billy

Sent from my iPhone

On Oct 9, 2012, at 6:45, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote:

> Hi all,
> 
> I am trying to generate histograms (in Stata 11.2) with age distributions for three categories overlaid in the same graph for different periods. Essentially I want to visually check whether the age distribution of the cohort in an age group changes between periods, and whether the distribution of sub groups of the population also change. 
> 
> I started off with -histogram- because this nicely collapses my patient level data, without me having to do this manually. However, while I found twoway to be an option to increase the number of series plotted on the graph, I guess what I'm really after are line plots which would allow transparency between the series.
> 
> I'm using the followinhg code to present single categories of interest (but for each level in my age group) and use the -by()- to present all periods on one combined graph (separate for each age group)
> 
> levelsof age_grp, local(levels)
> foreach l of local levels {
> histogram Age_At_Diag if age_grp==`l' & yydx!=., discrete percent /*
> */ yscale(range(20)) /* 
> */ ylabel(0(5)20 , gmax  angle(horizontal) format(%3.0f)) /*
> */ xtitle("Age at diagnosis") /*
> */ by(period, row(1) note("Graphs by period of diagnosis in `: label (age_grp) `l'' age group") /*
> */ t1title("Age distribution by diagnosis period",  size(medsmall)) legend(off)) /*
> */ name(graph`l', replace) 
> graph export Age_grp_distribution_`: label (age_grp) `l''.png, replace
> 
> }
> 
> 
> My questions are: 
> 
> Can I ask -histogram- to plot lines rather than bars?
> Can -histogram- (with lines if possible) plot more than 2 series of data
> 
> If -histogram- will not do this, what is a better method of doing this?
> 
> Best wishes
> 
> Tim
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