Prevent plot.gam from producing a figure

Question

Say, I have a GAM that looks like this:

# Load library
library(mgcv)

# Load data
data(mtcars)

# Model for mpg
mpg.gam <- gam(mpg ~ s(hp) + s(wt), data = mtcars)

Now, I'd like to plot the GAM using ggplot2 . So, I use plot.gam to produce all the information I need, like this:

foo <- plot(mpg.gam)

This also generates an unwanted figure. (Yes, I realise that I'm complaining that a plotting function plots something...) When using visreg in the same way, I'd simply specify plot = FALSE to suppress the figure, but plot.gam doesn't seem to have this option. My first thought was perhaps invisible would do the job (eg, invisible(foo <- plot(mpg.gam)) ), but that didn't seem to work. Is there an easy way of doing this without outputting the unwanted figure to file?

Answer 1

Okay, so I finally figured it out 5 minutes after posting this. There is an option to select which term to plot (eg, select = 1 is the first term, select = 2 is the second), although the default behaviour is to plot all terms. If, however, I use select = 0 it doesn't plot anything and doesn't give an error, yet returns exactly the same information. Check it out:

# Load library
library(mgcv)

# Load data
data(mtcars)

# Model for mpg
mpg.gam <- gam(mpg ~ s(hp) + s(wt), data = mtcars)

# Produces figures for all terms
foo1 <- plot(mpg.gam)

# Doesn't produce figures
foo2 <- plot(mpg.gam, select = 0)

# Compare objects
identical(foo1, foo2)

[1] TRUE

Bonza!