Changing axis titles for autoplot

Question

Using autoplot from ggfortify to create diagnostic plots:

library(ggplot2)
library(ggfortify)

mod <- lm(Petal.Width ~ Petal.Length, data = iris)
autoplot(mod, label.size = 3)

Is it possible to change the axis and plot titles (easily)? I'd like to translate them.

Answer 1

The function autoplot.lm returns an S4 object (class ggmultiplot, see ?`ggmultiplot-class`). If you look at the helpfile, you'll see they have replacement methods for individual plots. That means you can extract an individual plot, modify it, and put it back. For example:

library(ggplot2)
library(ggfortify)

mod <- lm(Petal.Width ~ Petal.Length, data = iris)
g <- autoplot(mod, label.size = 3) # store the ggmultiplot object

# new x and y labels
xLabs <- yLabs <- c("a", "b", "c", "d")

# loop over all plots and modify each individually
for (i in 1:4)
    g[i] <- g[i] + xlab(xLabs[i]) + ylab(yLabs[i])

# display the new plot
print(g) 

Here I only modified the axis labels, but you change anything about the plots individually (themes, colors, titles, sizes).

Answer 2

The solutions proposed by @user20650 are interesting and elegant.

Here is a less elegant solution based on myautoplot, a modified version of autoplot. I hope it can help you.
Download the myautoplot funtion here and save it in your working directory with the name myautoplot.r.
Then, use the following code:

library(ggplot2)
library(ggfortify)

source("myautoplot.r")
mod <- lm(Petal.Width ~ Petal.Length, data = iris)

####
# Define x-labels, y-labels and titles
####
# Residuals vs Fitted Plot
xlab_resfit <- "Xlab ResFit"
ylab_resfit <- "Ylab ResFit"
title_resfit <- "Title ResFit"

# Normal Q-Q Plot
xlab_qqplot <- "Xlab QQ"
ylab_qqplot <- "Ylab QQ"
title_qqplot <- "Title QQ"

# Scale-Location Plot
xlab_scaleloc <- "Xlab S-L"
ylab_scaleloc <- "Ylab S-L"
title_scaleloc <- "Title S-L"

# Cook's distance Plot
xlab_cook <- "Xlab Cook"
ylab_cook <- "Ylab Cook"
title_cook <- "Title Cook"

# Residuals vs Leverage Plot
xlab_reslev <- "Xlab Res-Lev"
ylab_reslev <- "Ylab Res-Lev"
title_reslev <- "Title Res-Lev"

# Cook's dist vs Leverage Plot
xlab_cooklev <- "Xlab Cook-Lev"
ylab_cooklev <- "Ylab Cook-Lev"
title_cooklev <- "Title Cook-Lev"

# Collect axis labels and titles in 3 lists    
xlab_list <- list(resfit=xlab_resfit, qqplot=xlab_qqplot, 
      scaleloc=xlab_scaleloc, cook=xlab_cook, reslev=xlab_reslev,
      cooklev=xlab_cooklev)
ylab_list <- list(resfit=ylab_resfit, qqplot=ylab_qqplot, 
      scaleloc=ylab_scaleloc, cook=ylab_cook, reslev=ylab_reslev,
      cooklev=ylab_cooklev)
title_list <- list(resfit=title_resfit, qqplot=title_qqplot, 
      scaleloc=title_scaleloc, cook=title_cook, reslev=title_reslev,
      cooklev=title_cooklev)

# Pass the lists of axis labels and title to myautoplot
myautoplot(mod, which=1:6, xlab=xlab_list, 
                           ylab=ylab_list, 
                           title=title_list)