*- 三维图形 3D 图形
clear
set obs 900
gen x = int((_n - mod(_n-1,30) -1 ) /30 )
gen y = mod(_n-1,30)
gen z = normalden(x,10,3)*normalden(y,15,5)
surface x y z
clear
set obs 2000
gen x = int((_n - mod(_n-1,30) -1 ) /30 )
gen y = mod(_n-1,30)
gen z = normalden(x,10,2)*normalden(y,15,1)*normalden(y,5,10)
surface x y z
这个怎么用呢? 直接copy做命令么? n ,30,15要不要改的? 虚心请教