Controlling the size and number of graphs per pdf page generated by ggplot loop in R markdown

4
votes

I would like to generate a pdf document, using R markdown, to display a series of plots made using ggplot in a for loop. Is it possible to control number of plots on each page so there is, for example, a 2 X 2 grid of plots per page?

I'd like to maintain the flexibility so that I can change the total number of graphs, so that it splits across the appropriate number of pages.

My attempt using ggplot2 and gridExtra packages is below, but I can't control the number of graphs per page, it seems to want to squeeze them on to a sinlge page only. I've tried changing the ncol,nrow,heights,widths arguments in grid.arrange but it doesn't seem to help. 

    ---
    title: "ggplot Layout"
output: pdf_document
    ---

    ```{r,figure2 fig.height=8, fig.width=6,echo=FALSE,message=FALSE}


    library(ggplot2)
    library(gridExtra) 

    graphlist<-list()
    count <- 1
    colnums<-c(1,5,6,7,8,9,10)

    for (i in colnums) {
    plot.x.name<-names(diamonds[i])
    p <- ggplot(data=diamonds,aes_string(x = plot.x.name)) + geom_histogram() 
    graphlist[[count]]<-p
    count <- count+1

    }

    do.call("grid.arrange",c(graphlist,ncol=2))



    ```

The type of thing I'm looking for is demonstrated by this code (adapted from http://kbroman.github.io/knitr_knutshell/pages/figs_tables.html), but this doesn't work with ggplot, unfortunately. 

---
title: "Example Layout"
output: pdf_document
---


```{r bunch_o_figs,fig.height=8, fig.width=6, message=FALSE,echo=FALSE}
n <- 100
x <- rnorm(n)
par(mfrow=c(2,2), las=1)
for(i in 1:20) {
  y <- i*x + rnorm(n)
  plot(x, y, main=i)
}
``
1
rggplot2knitrpandocgridextra

1 Answers

6
votes

You could try marrangeGrob

---
title: "ggplot Layout"
output: pdf_document
---

```{r figure2 , fig.height=8, fig.width=6,echo=FALSE,message=FALSE}


    library(ggplot2)
    library(gridExtra) 

    graphlist <- replicate(10, qplot(1,1), simplify = FALSE)

    do.call("marrangeGrob",c(graphlist,ncol=2,nrow=2))
```