# load data
data(nox)

# fit model with interaction and obtain diagnostics
fit.nox<-ssanova(log10(nox)~comp*equi,data=nox)
sum.nox<-summary(fit.nox,TRUE)
round(sum.nox$kappa,2)
round(sum.nox$pi,2)
round(sum.nox$cos,2)

# fit cubic spline in equi and plot
fit.nox<-ssanova(log10(nox)~equi,data=nox,met="m")
grid<-sort(nox$equi)
est<-predict(fit.nox,data.frame(equi=grid),se=TRUE)
plot(nox$equi,log10(nox$nox),xlab="equivalence ratio",
     ylab=expression(log[10](NO[x])))
lines(grid,est$fit,col=4)
lines(grid,est$fit+1.96*est$se,col=5)
lines(grid,est$fit-1.96*est$se,col=5)