Re: st: overlapping histograms

[Nick Cox <n.j.cox@stata.com>]

It is good to know that you can do this. My guess is that many users 
would like to see it written up somewhere.

However, these histograms tend to lead only to crude inferences. Users 
can't read off quantitative conclusions from the graph, just stuff like 
"The distributions are about the same", or "... very different", etc.

Compare the road that begins

. separate mpg, by(foreign) veryshortlabel

. qqplot mpg1 mpg0

. qqplot mpg1 mpg0, xsc(log) ysc(log)

That is the start of a story: the distributions differ multiplicatively,
etc. Numbers can be then worked out.

Nick

Svend Juul wrote:

> Jeph wrote - in a comment to several suggestions:
>
> More like this:
>
> sysuse auto
>
> twoway ///
> (histogram mpg if foreign, bin(10) gap(5) fc(gray) lc(black)) ///
> (histogram mpg if !foreign, bin(10) gap(15) fc(white) lc(black)) ///
>    legend(off)
>
> It works better when there are more bins, ie, more obs - I have 100k
> obs so I have lots of thin bars. The effect is quite good, though
> I dislike that, as here, one distribution has thinner bars than the
> other.
>
> ================================================================
>
> Fascinating game. How about this?
>
> twoway ///
> (histogram mpg if !foreign, start(10) width(2) fc(white) lc(black)) ///
> (histogram mpg if foreign, gap(50) fc(gray) lc(black) start(10)
> width(2)) ///
>    , legend(off) plotregion(margin(b=0))
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