*! version 1.34 am 25Nov99  (STB-54: gr43)
program define overlay
	version 6.0
	syntax [varlist] [if], BY(string) [SAVING(string) FUNCtion(string) YLAB(numlist) XLAB(numlist) DEBUG ROUND(real 0.001) *]
	local gopt "`options'"	
	tokenize "`varlist'"
preserve

if "`if'"~="" {
	keep `if'
}


if "`func'"~="" {
   di "Sometimes overlay.ado will fail to give you the correct graph"
   di "This is due to selecting a function that is not graph"
   di 
   di " The user may have to select XLAB and YLAB options that do not change by group"
   di "See also the end Diagnostics"
}

***********************************************
* How many levels does the by variable have 
* and put them into the matrix mine
***********************************************

tempvar bygrp

if "`by'"~="" {
	sort `by'
	qui by `by': gen `bygrp'=cond(_n==1,1,.)
	qui replace `bygrp'=sum(`bygrp')
	local bylev = `bygrp'[_N]
}

***********************************************
* Saving the file or not.
* NB if file exists it is deleted!!
***********************************************

	if ("`saving'"~="") {
		cap confirm new file `saving'.gph
		if _rc~=0 {
			di "Deleteing file...`saving'.gph"
			!rm `saving'.gph
		}
		di "Saving file... `saving'.gph"
		gph open, saving(`saving')
	}
	else { gph open }

if "`debug'"~="" { gph close }

***********************************************
* Loop through all the levels of the 
* by variable
***********************************************

local pen 1

local i 1
while `i' <= `bylev' {

	local pen=`pen'+1
	local pen= mod(`pen',10)

	if "`ylab'"=="" {
		summ `1'
		local min=string(round(r(min),`round'))
		local max=string(round(r(max),`round' ))
		local mid=string(round(r(mean),`round' ))
		local ylab = "`min',`mid',`max'"
	}
	if "`xlab'"=="" {
		summ `2'
		local min=string(round(r(min),`round' ))
		local max=string(round(r(max),`round' ))
		local mid=string(round(r(mean),`round' ))
		local xlab = "`min',`mid',`max'"
	}

	if "`function'"=="" { 
		graph `varlist' if `bygrp'==`i', xlab(`xlab') ylab(`ylab') pen(`pen') `gopt'
	}
	else {
	   cap `function' `varlist' if `bygrp'==`i', pen(`pen') xlab(`xlab') ylab(`ylab') `gopt'
           if _rc~=0 {
              local warning "Pen option not working Lines will not be distinct"
	      cap `function' `varlist' if `bygrp'==`i', xlab(`xlab') ylab(`ylab') `gopt'
              if _rc~=0 {
               local warning "Pen and xlab/ylab options do not work hence the y and x scales might be wrong in the composite graph"
di "`function' `varlist' if `bygrp'==`i', `gopt'"

               sto
 `function' `varlist' if `bygrp'==`i', `gopt'
ston
              }
           }
	}


local i = `i'+1
}



gph close

restore

if "`warning'"~="" {
    di "Extra Diagnostic errors"
    di "-----------------------"
    di "`warning'"
}
end