Annotating in GRAPH3D

[Iuri Gavronski]

I am trying to use GRAPH3D to plot and I need some help to annotate the graph. For example, would be useful adding a reference plane, such as (x, y=0, z). I also would like to change the size of the labels. Help is appreciated.

I am including some example code here, in case someone wants to reproduce it:

set more off
/* load data */
clear
sysuse auto

set matsize 11000
center price mpg length, standardize replace

/* estimate model: CHANGE MODEL HERE */
reg c_price i.foreign##c.c_mpg##c.c_mpg i.foreign##c.c_length##c.c_length

summ price foreign mpg length

/* specify values of x and y at which margins are calculated: CHANGE VALUES HERE */
local xfrom -1
local xto   1    
local xstep .1

local zfrom -1
local zto   1
local zstep .1

/* post margins in matrix e(b) at specified values of the x and y variables: CHANGE VARIABLE FOR MARGINAL EFFECT HERE */
margins i.foreign, at(c_mpg=(`xfrom'(`xstep')`xto') c_length=(`zfrom'(`zstep')`zto')) post

/* construct variable z */
mat b = e(b)
mat mgns = b[1...,1...]'
svmat double mgns, name(mgn)
ren mgn1 y
replace y=y*1 /* scale z variable to make it more visible: CHANGE SCALING HERE */
summ y

/* construct variables x and z -- observe that the response variable is y (not z) */
gen x = .
gen z = .
gen m = .

local pos=1
forv lx = `xfrom'(`xstep')`xto' {
    forv lz = `zfrom'(`zstep')`zto' {
        forv lm =0(1)1 {
            local lx = round(`lx',.0001)
            local lz = round(`lz',.0001)
            qui replace x = `lx' in `pos'
            qui replace z = `lz' in `pos'
            qui replace m = `lm' in `pos'
            local pos=`pos'+1
        }
    }
}

/* plot variables x, y, and z: CHANGE OPTIONS HERE */
graph3d x y z m, ///
    ///xangle(88) yangle(179) zangle(45) xcam(-30) zcam(200) ///
    aspectratio(1) ///
    mark cuboid innergrid blv perspective colorscheme(cr) ///
    /// xlang(90) ylang(30) zlang(-12) xlpos(9) ylpos(4) zlpos(12) ///
    /// xang(15) yang(80) ///
    xlab("mpg") ylab("length") zlab("price") ///
    /// xlang(315) ylang(90) zlang(0) ///
    /// xlpos(11) ylpos(3) zlpos(11) ///
    markeroptions(msize(tiny))
graph export "car_prices.png", replace