# meanspv: Compute Mean Spherical SPV In vdg: Variance Dispersion Graphs and Fraction of Design Space Plots

 meanspv R Documentation

## Compute Mean Spherical SPV

### Description

Computes the matrix of spherical region moments for a given model formula and a vector of radii, and uses this to calculate the mean spherical SPV for each of the radii. The function `expmat` calculates the matrix containing the exponents of each model factor within each model term as columns. Only simple formulae are allowed for. Only products of terms should be included in calls to `I`. The power operator `^` should be used instead of `sqrt`. Models should contain only monomial terms.

### Usage

```meanspv(formula, radii, FtF.inv, n)

expmat(formula)
```

### Arguments

 `formula` model formula `radii` numeric vector or radii at which to calculate the matrix of spherical region moments `FtF.inv` inverse of F'F, where F is the design matrix `n` integer giving the number of design runs

### Author(s)

Pieter C. Schoonees

### References

Pieter C. Schoonees, Niel J. le Roux, Roelof L.J. Coetzer (2016). Flexible Graphical Assessment of Experimental Designs in R: The vdg Package. Journal of Statistical Software, 74(3), 1-22. doi: 10.18637/jss.v074.i03.

### Examples

```f1 <- formula(~ x1*x2)
expmat(f1)
f2 <- update(f1, ~ . + I(x1^2) + I(x2^2))
expmat(f2)
f3 <- update(f2, ~ . + I(x2^0.4))
expmat(f3)
f4 <- update(f3, ~ . + I(x1^2):I(x2^2))
expmat(f4)
f5 <- update(f4, ~ . + I(x1^3*x2^0.5))
expmat(f5)
```

vdg documentation built on July 8, 2022, 1:08 a.m.