```
# NOT RUN {
# 2-factor example
# ----------------
T <- c(-1, +1, -1, +1) # centered and scaled temperature
S <- c(-1, -1, +1, +1) # centered and scaled speed variable
y <- c(69, 60, 64, 53) # conversion, is our response variable, y
doe.model <- lm(y ~ T + S + T * S) # model with main effects, and interaction
contourPlot(doe.model)
# 3-factor example
# ----------------
data(pollutant)
mod.full <- lm(y ~ C*T*S, data=pollutant)
contourPlot(mod.full, N=50) # high resolution plot
contourPlot(mod.full, xlab='C', ylab='S',
main="Strong C:S interaction",
colour.function=rainbow)
# Central composite design
P <- c(-1, +1, -1, +1, 0, -1.41, 0, +1.41)
T <- c(-1, -1, +1, +1, +1.41, 0, -1.41, 0)
y <- c(715, 713, 733, 725, 738, 717, 721, 710)
mod.CCD <- lm(y ~ P*T + I(P^2) + I(T^2))
contourPlot(mod.CCD, 'P', 'T', xlim=c(-2.2, 2.2), ylim=c(-3,2))
# }
```

Run the code above in your browser using DataLab