surface.stats: Statistics of Quadratic Response Surface

Description

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.

Usage

surface.stats(obj)
surface.stats.main(b, xlim, ylim)

Arguments

obj

an object of class siRSM, often the result of siRSM

coefficients of the response surface, e.g., obj$coef where obj is an object of class siRSM

xlim

x-boundaries in 3D (x,y,z)-perspective plot --- used when surface.stats.main is called internally by plot.siRSM

ylim

y-boundaries in 3D (x,y,z)-perspective plot --- used when surface.stats.main is called internally by plot.siRSM

Value

u0: x-coordinates of surface's stationary point
v0: y-coordinates of surface's stationary point
p10: intercept in xy-plane of surface's 1st principal axis
p11: slope in xy-plane of surface's 1st principal axis
p20: intercept in xy-plane of surface's 2nd principal axis
p21: slope in xy-plane of surface's 2nd principal axis
ax.congr: slope of surface along the congruence line, u-v=0
ax2.congr: curvature of surface along the congruence line, u-v=0
ax.incongr: slope of surface along the incongruence line, u+v=0
ax2.incongr: curvature of surface along the incongruence line, u+v=0
pl: intersection of 1st axis at lower border, to be used by plot.siRSM
ph: intersection of 1st axis at upper border, to be used by plot.siRSM
sl: intersection of 2nd axis at lower border, to be used by plot.siRSM
sh: intersection of 2nd axis at upper border, to be used by plot.siRSM

References

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.), Jossey-Bass, pp. 350-400.