R/multiplot.R

Defines functions multiplot

Documented in multiplot

#' Multiple plot function
#'
#' ggplot objects can be passed in ..., or to plotlist (as a list of ggplot objects)
#' - cols:   Number of columns in layout
#' - 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.
#'       
#'@param ggplotobject ggplotobjects
#'@param cols  Number of columns in layout
#'@param layout A matrix specifying the layout. If present, 'cols' is ignored.
#'@return plot
#'@examples
#'multiplot(p1, p2, p3, p4, cols=2)
#'
#'@export 
#'@name multiplot
#' 
#'
multiplot <- function(..., plotlist=NULL, file, cols=1, layout=NULL) {
        require(grid)
        
        # 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))
                }
        }
}
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