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Re: st: easy histogram

From (Jeff Pitblado, Stata Corp.)
Subject   Re: st: easy histogram
Date   Fri, 28 Feb 2003 18:25:54 -0600

David Airey <david.airey@Vanderbilt.Edu> asks about the -xscale(log)- option
with easy graphs:

> I'm curious why there is an xscale(log) option in the easy histogram dialog.
> When I do:

> clear
> sysuse auto
> histogram mpg, saving(h1, replace)
> histogram mpg, xscale(log) saving(h2, replace)
> gen logmpg = log(mpg)
> histogram logmpg, saving(h3, replace)
> graph combine h1.gph h2.gph h3.gph

> I get what I expect in the first and third histogram commands, but not the
> second. The bars are stretched widthwise in the second histogram, such that
> I don't think the density adds to 1. In some twoway commands, changing the
> xscale to log when you have estimated a model on x and not log(x) is an
> incorrect procedure. Is this another instance? If so, I think it should be
> disallowed. Easy graph dialogs should be easy.

After receiving a reply from an email he sent to Stata's Technical Support,
David then asks:

> But does it _ever_ make sense to include this as an option for the histogram
> command? In twoway scatter it does, but in histogram it doesn't, since the
> area will not sum to 1. Am I wrong?

David makes a good point for removing the option for -histogram-, and we will
remove the checkboxes for log scales from the easy graph dialog for

However, the "full featured" dialog for -histogram- will remain the same since
both -xscale(log)- and -yscale(log)- are valid -graph twoway- options.

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