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RE: st: Plotting 3way interactions

From   "Nick Cox" <>
To   <>
Subject   RE: st: Plotting 3way interactions
Date   Tue, 18 Aug 2009 16:59:53 +0100

One issue, perhaps the only one, is the use of -csocanx- on the RHS of
calls to -twoway function-. That is not how the command works: it
expects a generic -x- to be used as argument. See the help.


Philip Ender

I believe that Kris is referring to a FAQ page posted on ATS' Stata
Faq page.  I am working with him off line to see if we can solve the
problem.  When (if) we find the solution I'll report back to

Kris Anderson wrote

I am struggling with a final line of code on plotting a 3way
interaction in Stata. I can run everything except the two-way code for
the scatter plot (I added ** to identify the line below). What I get
is a mix of lines, not the lovely interaction plot from the FAQ. Any

regress avgdrink age sex gradedich white hisp csocanx caffil cpn SAF
SP AP SAP if currentdrinker > 0
sum csocanx
sum csocanx
global hi=r(max)
global lo=r(min)
sum caffil
global HAF=r(mean)+r(sd)
global LAF=r(mean)-r(sd)
sum cpn
global HPN=r(mean) +r(sd)
global LPN=r(mean) -r(sd)
sum age
global mage=r(mean)
sum gradedich
global mgrade=r(mean)
sum white
global mwhite=r(mean)
sum hisp
global mhisp=r(mean)
global HPNHAF "csocanx + ($HPN)*SP + ($HAF)*SAF + ($HPN)*($HAF)*SAP"
global HPNLAF "csocanx + ($HPN)*SP + ($LAF)*SAF + ($HPN)*($LAF)*SAP"
global LPNHAF "csocanx + ($LPN)*SP + ($HAF)*SAF + ($LPN)*($HAF)*SAP"
global LPNLAF "csocanx + ($LPN)*SP + ($LAF)*SAF + ($LPN)*($LAF)*SAP"
lincom $HPNHAF
global b1 = r(estimate)
lincom $HPNLAF
global b2 = r(estimate)
lincom $LPNHAF
global b3 = r(estimate)
lincom $LPNLAF
global b4 = r(estimate)
lincom _cons + $HPN*cpn + $HAF*caffil + $HPN*$HAF*AP + $mage*age +
$mgrade*gradedich + $mwhite*white
global c1 = r(estimate)
lincom _cons + $HPN*cpn + $LAF*caffil + $HPN*$LAF*AP + $mage*age +
$mgrade*gradedich + $mwhite*white
global c2 = r(estimate)
lincom _cons + $LPN*cpn + $HAF*caffil + $LPN*$HAF*AP + $mage*age +
$mgrade*gradedich + $mwhite*white
global c3 = r(estimate)
lincom _cons + $LPN*cpn + $LAF*caffil + $LPN*$LAF*AP + $mage*age +
$mgrade*gradedich + $mwhite*white
global c4 = r(estimate)
***twoway(function y=$c1+$b1*csocanx, range($lo $hi))(function
y=$c2+$b2*csocanx, range($lo $hi))(function y=$c3+$b3*csocanx,
range($lo $hi))(function y=$c4+$b4*csocanx, range($lo $hi))(scatter
avgdrink cpn, msym(oh) jitter(3)), legend(order(1 "1 HPNHAF" 2 "2
HPNLAF" 3 "3 LAPHAF" 4 "4 LAPLAF")) xtitle (X) ytitle(Y)
name(con3wayb, replace)
lincom ($HPNHAF)- ($HPNLAF)
lincom ($HPNHAF)- ($LPNHAF)
lincom ($HPNLAF)- ($LPNLAF)
lincom ($LPNHAF)- ($LPNLAF)
lincom ($HPNHAF)- ($LPNLAF)
lincom ($HPNLAF)- ($LPNHAF)

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