labeling axis for parametric terms with plot.gam

Question

I am trying to plot my gam results. The plotting works very well for all the smooth terms (in my case terms 1 to 8) but if I want to plot parametric terms (from 9 onwards), I can't change the axis labels. No matter if I use plot, plot.gam, termplot or text I can't do it. Any tips? Below is the code example

par(mfrow=c(3,3), oma=c(1,1,1,1),pty="s",mar=c(4.5,4.5,1,1)) 
# the first three graphs work perfectly
plot.gam(model$gam,select=1,scale=0,pers=TRUE,all.terms=T,shade=T,xlab="Water depth",ylab="") 
plot.gam(model$gam,select=2,scale=0,pers=TRUE,all.terms=T,shade=T,xlab="Bottom current speed",ylab="")
plot.gam(model$gam,select=3,scale=0,pers=TRUE,all.terms=T,shade=T,xlab="Substance",ylab="")
# this graph for the parametric term is plotted but I cannot change axis labels
plot.gam(model$gam,select=9,scale=0,pers=T,all.terms=T,shade=T,xlab="AIS",ylab="")

Answer 1

If you are using RStudio you can check the source code of plot.gam by hitting the F2 button. In R execute the plot.gam without brackets. Then you can find, that plot() is replaced by termplot() for some select values. Thus, to maipulate the x-axis labels you have to use xlabs instead of xlab .

require(mgcv) 
pa <- c(1, rep(0, 9))
term_A <- runif(10, 9, 15)
term_B <- runif(10, 1, 25)
data <- as.data.frame(cbind(pa, term_A, term_B)) 
mod <- gam(pa ~ s(term_A, k=3) + term_B, family=binomial, data=data) 
summary(mod)
par(mfrow=c(2, 2)) 
# xlab=""
plot.gam(mod, select=1, all.terms=T, shade=T, xlab="your own lab title", ylab="") 
# xlabs=""
plot.gam(mod, select=2, all.terms=T, shade=T, xlabs="your own lab title", ylab="")