R/multiplot.R

In bi-sdal/sdalr: Convenience functions for the Social and Decision Analytics Lab

library(grid)

#' Multiple plot function
#'
#' This function is taken from the R Graphics Coookbook by Winston Chang.
#' It lays out multiple ggplot objects into a single figure.
#' @param ... ggplot objects
#' @param plotlist if individual ggplot objects are not passed into \code{...},
#'                 then a \code{list} of ggplot objects can also be passed
#' @param file file?
#' @param cols number of columns used to layout the plots, defaults to \code{`1`}
#' @param layout a matrix specifying the layout. If present, 'cols' is ignored.
#'               If the layout is something like matrix(c(1,2,3,3), nrow=2, byrow=TRUE),
#'               then plot 1 will go in the upper left, 2 will go in the upper right,
#'               and 3 will go all the way across the bottom.
#'
#' @export
multiplot <- function(..., plotlist=NULL, file, cols=1, layout=NULL) {
    # Make a list from the ... arguments and plotlist
    plots <- c(list(...), plotlist)

    numPlots = length(plots)

    # If layout is NULL, then use 'cols' to determine layout
    if (is.null(layout)) {
        # Make the panel
        # ncol: Number of columns of plots
        # nrow: Number of rows needed, calculated from # of cols
        layout <- matrix(seq(1, cols * ceiling(numPlots/cols)),
                         ncol = cols, nrow = ceiling(numPlots/cols))
    }

    if (numPlots == 1) {
        print(plots[[1]])

    } else {
        # Set up the page
        grid.newpage()
        pushViewport(viewport(layout = grid.layout(nrow(layout), ncol(layout))))

        # Make each plot, in the correct location
        for (i in 1:numPlots) {
            # Get the i,j matrix positions of the regions that contain this subplot
            matchidx <- as.data.frame(which(layout == i, arr.ind = TRUE))

            print(plots[[i]], vp = viewport(layout.pos.row = matchidx$row,
                                            layout.pos.col = matchidx$col))
        }
    }
}