st: graph rarea optical illusion or coding error?

[Ulrich Kohler <kohler@wzb.eu>]

Listers,

I try to create a figure of shaded areas for 5%, 10%, 15% ... 95%
confidence intervals. The resulting areas seem to have a lines around
the areas that are darker than both neighbouring areas. Is it possible
to get rid of this, or is this just an optical illusion?

Here is a minimal example of my code. Note that I tried various settings
for -lwidht()- , -lcolor()-, -fintensity()-. Most surprisingly
-lcolor(none)- removes areas completely, btw.

-----------------------------------------------------illusion.do
sysuse auto, clear

collapse (mean) mean=mpg (semean) se=mpg, by(rep78)

local pen 15
forv alpha = .05(.06).95 {
	gen ub`pen' = mean + invnormal(1-`alpha'/2)*se
	di "gen ub`pen' = mean + `=invnormal(1-`alpha'/2)'*se"
	gen lb`pen' = mean - invnormal(1-`alpha'/2)*se
	local pen = `pen'-1
}

forv i = 15(-1)1 {
	  local rarea `rarea'	       ///  
	  || rarea ub`i' lb`i' rep78,  ///		
	  lcolor(gs`i') fcolor(gs`i') lwidth(none) sort
}

graph twoway `rarea' || , legend(off)

exit
-------------------------------------------------------------------






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