Random graphs (19): Simple interaction plots with -marginsplot- for continuous variables

sysuse auto, clear

regress mpg c.weight##c.gear_ratio

// Obtain means and standard deviation for plots
qui sum weight
local w_minsd = r(mean) - r(sd)
local w_mean  = r(mean)
local w_plusd = r(mean) + r(sd)

qui sum gear_ratio
local g_minsd = r(mean) - r(sd)
local g_mean  = r(mean)
local g_plusd = r(mean) + r(sd)

// Calculate predicted values for plot
margins, at(c.gear_ratio = (`g_minsd' `g_mean' `g_plusd') ///
            c.weight = (`w_minsd' `w_mean' `w_plusd')) vsquish
// Plot
marginsplot, recastci(rarea) ciopts(color(gs10)) ///
   title("Weight moderates the gear ratio{char 0150}mileage association") ///
   xlabel(`g_minsd' "-1 SD" `g_mean' "Average gear ratio" `g_plusd' "+1 SD") ///
   ytitle("Predicted mileage") ///
   xtitle("Gear ratio") ///
   plotopts(msymbol(none)) ///        // Turn off markers
   plot1opts(lpattern(longdash)) ///  // Define line types here
   plot2opts(lpattern(solid)) ///
   plot3opts(lpattern(shortdash)) ///
   legend(subtitle(Weight) ///
   order(4 "- 1 SD" 5 "Mean" 6 "+ 1 SD" 2 "95% CI"))
        // For some reason, marginsplot ignores the -label option-, therefore
        // -order- is used here
gr export plot.png, as(png) replace

Random graphs (18): Simple interaction plots with -marginsplot- for categorical and continuous variables

sysuse auto, clear

reg mpg c.weight##i.foreign

qui sum weight

local minsd = r(mean) - r(sd)
local mean  = r(mean)
local plusd = r(mean) + r(sd)

margins foreign, at(weight = (`minsd' `mean' `plusd'))

marginsplot, recast(line) noci scheme(lean1) ///
             name(first, replace)
gr export first.png, as(png) replace
// Impossible to tell the difference between
// domestic and foreign lines because of the lean scheme

marginsplot, recast(line) noci ///
             plot1opts(lpattern(dash)) ///
             scheme(lean1) ///
             name(second, replace)
gr export second.png, as(png) replace
// That fixes the problem

marginsplot, recast(line) recastci(rarea) ciopts(color(gs10)) ///
             plot1opts(lpattern(dash)) ///
             scheme(lean1) ///
             name(third, replace)
gr export third.png, as(png) replace
// That's a nice way of plotting CI's

marginsplot, recast(line) recastci(rarea) ciopts(color(gs10)) ///
             plot1opts(lpattern(dash)) ///
             ytitle("Predicted mileage") ///
             title("Car type moderates the weight{char 0150}mileage association") ///
             xlabel(`minsd' "-1 SD" `mean' "Average weight (lbs.)" `plusd' "+1 SD") ///
             xtitle("") ///
             scheme(lean1) ///
             name(fourth, replace)
gr export fourth.png, as(png) replace
// That labels the graph nicely