Creating Page Titles for Multi-Page PDFs in R using MarrangeGrob and ggsave

In this tutorial, we will explore how to create custom page titles for multi-page PDFs in R using the marrangeGrob and ggsave functions from the gridExtra package. We will also discuss ways to customize the appearance of these titles.

Introduction

The marrangeGrob function is used to arrange multiple plots or graphics objects into a single grob object, which can then be saved as a PDF file using the ggsave function. By default, this grob object includes page numbers at the top of each page. However, we can customize these titles by passing a quoted expression to the top parameter when calling marrangeGrob. In this tutorial, we will explore how to create custom page titles for multi-page PDFs in R using marrangeGrob and ggsave.

Sample Data

To demonstrate the concept of creating custom page titles for multi-page PDFs, let’s start with some sample data. We’ll use the built-in mtcars dataset from R and create a few plots using the ggplot2 package.

# Load required libraries
library(ggplot2)
library(gridExtra)

# Create some plots
p1 <- qplot(mpg, wt, data = mtcars, colour = cyl)
p2 <- qplot(mpg, data = mtcars) + ggtitle("Title 1")
p3 <- qplot(mpg, data = mtcars, geom = "dotplot")

# Combine into a list
plots <- list(p1, p2, p3)

# Create a character vector of plot names
plot_names <- c("Plot 1", "Plot 2", "Plot 3")
names(plots) <- plot_names

# Export to a PDF file
Export <- gridExtra::marrangeGrob(plots, nrow = 1, ncol = 1,
                                  top=quote(names(plots)[g]))

Understanding the top Parameter

The top parameter in the marrangeGrob function is used to specify a quoted expression that will be evaluated for each plot. This expression should return a string that will be displayed at the top of each page.

By default, the top parameter uses a built-in expression that includes the current plot index (g) and the total number of plots (npages). However, we can customize this behavior by passing our own quoted expression to the top parameter.

Customizing Page Titles

To create custom page titles, we need to extract the values from the plot_names vector. We can do this by using the names(plots)[g] expression in the top parameter.

# Create a PDF file with custom page titles
Export <- gridExtra::marrangeGrob(plots, nrow = 1, ncol = 1,
                                  top=quote(names(plots)[g]))
ggsave(filename = "custom_page_titles.pdf", Export, scale = 1.5)

Using Other Customization Options

While the top parameter is useful for creating custom page titles, there are other ways to customize the appearance of these titles.

One option is to use the textGrob function to create a text object that will be displayed at the top of each page. We can do this by passing a quoted expression to the top parameter and using the textGrob function to create the text object.

# Create a PDF file with custom page titles using textGrob
Export <- gridExtra::marrangeGrob(plots, nrow = 1, ncol = 1,
                                  top=quote(textGrob(paste0("Plot ", names(plots)[g]), fontface = "bold", size = 24)))
ggsave(filename = "custom_page_titles_text.pdf", Export, scale = 1.5)

Conclusion

In this tutorial, we explored how to create custom page titles for multi-page PDFs in R using the marrangeGrob and ggsave functions from the gridExtra package. We discussed ways to customize these titles by passing quoted expressions to the top parameter and used examples to demonstrate the concept.

By following the steps outlined in this tutorial, you should be able to create custom page titles for your multi-page PDFs using R. Whether you’re creating reports or presentations, customizing page titles can help improve the overall appearance of your documents.

Last modified on 2025-05-07