# surface.stats: Statistics of Quadratic Response Surface In siRSM: Single-Index Response Surface Models

## 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

 ```1 2``` ```surface.stats(obj) surface.stats.main(b, xlim, ylim) ```

## Arguments

 `obj` an object of class `siRSM`, often the result of `siRSM` `b` 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`

## Author(s)

Huan Cheng, Mu Zhu

## 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.

siRSM documentation built on May 29, 2017, 10:54 a.m.