Computes stationary point, 1st and 2nd principal axes of the quadratic response surface, shapes and curvatures along the congruence and incongruence lines, as well as various parameters useful for plot.siRSM
.
1 2  surface.stats(obj)
surface.stats.main(b, xlim, ylim)

obj 
an object of class 
b 
coefficients of the response surface, e.g., 
xlim 
xboundaries in 3D (x,y,z)perspective plot — used when 
ylim 
yboundaries in 3D (x,y,z)perspective plot — used when 
u0 
xcoordinates of surface's stationary point 
v0 
ycoordinates of surface's stationary point 
p10 
intercept in xyplane of surface's 1st principal axis 
p11 
slope in xyplane of surface's 1st principal axis 
p20 
intercept in xyplane of surface's 2nd principal axis 
p21 
slope in xyplane of surface's 2nd principal axis 
ax.congr 
slope of surface along the congruence line, 
ax2.congr 
curvature of surface along the congruence line, 
ax.incongr 
slope of surface along the incongruence line, 
ax2.incongr 
curvature of surface along the incongruence line, 
pl 
intersection of 1st axis at lower border, to be used by 
ph 
intersection of 1st axis at upper border, to be used by 
sl 
intersection of 2nd axis at lower border, to be used by 
sh 
intersection of 2nd axis at upper border, to be used by 
Huan Cheng, Mu Zhu
Edwards JR (2002), "Alternatives to difference scores: Polynomial regression analysis and response surface methodology," in Measuring and Analyzing Behavior in Organizations: Advances in Measurement and Data Analysis (F. Drasgow, N. Schmitt, Eds.), JosseyBass, pp. 350400.
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