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st: RE: Graph matrix with non-linear regression lines


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Graph matrix with non-linear regression lines
Date   Thu, 12 Jun 2003 19:21:21 +0100

Bill Dupont
 
> In version 7, the -matrix- and -band- options of the graph 
> command gave
> matrix graphs with a non-linear regression line added to 
> each scatter
> plot.  These regression lines appear to be unavailable in 
> the version 8
> graph matrix command.  Assuming I have not misread the 
> manual, what are
> listers thoughts on the utility of these regression lines on matrix
> plots?  What were Stata's reasons for dropping this option? 
>  I thought it was useful.

-band()- showed conditional group medians. 
That's, I guess, a kind of L_1 regression. 

As you're polling, I hadn't noticed it had gone, 
despite using -graph matrix- quite a lot, so 
that's lukewarm at best. 

Why has it gone is a question for Stata Corp, 
but I note that -graph matrix- is in essence
a matrix of -scatter-. In principle, there 
are all sorts of graphs which can be put into 
a matrix, and while we're waiting for Stata 
Corp to give us some easy handles for that, 
a challenge is to see how far one can 
get. 

Below my signature is an example. This 
is just -my- -graph- -matrix- on 12 June. I 
decided to put quantile plots on the diagonal, 
and I prefer -lowess-, but the idea can 
be varied fairly easily. 

Nick 
n.j.cox@durham.ac.uk 

P.S. it's slow. (OK, now don't start that one again.)

program mygraphmatrix 
*! NJC 1.0.0 12 June 2003 
	version 8 
	syntax varlist(numeric) [if] [in] [, * ] 
	
	marksample touse
	qui count if `touse' 
	if r(N) == 0 error 2000 

	set graphics off 
	
	qui foreach y of local varlist {
		local ny = 1 
		foreach x of local varlist { 
			tempname f 
			if `ny' > 1 { 
				local yt
			} 
			else {
				local yt : variable label `y' 
				if `"`yt'"' == "" local yt "`y'"
			} 
			if "`x'" == "`y'" { 
				quantile `x', yti("`yt'") saving(`f'.gph)
			} 
			else { 
				lowess `y' `x', title("") note("") ///
				legend(off) ///
				yti(`"`yt'"') saving(`f'.gph) `options' 
			} 	
			local files `"`files' "`f'""' 
			local FILES "`FILES' `f'.gph" 
			local ny = `ny' + 1 
		}
	}

	set graphics on
	
	graph combine `files', imargin(zero) 
	
	foreach F in `FILES' { 
		erase `F'
	} 	
end 

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