27 Nov

Multiplot function for ggplot (with title)

Hi GISouille,

Here is a way to get a multiplot with ggplot.

library(ggplot2)
 
for (i in 1:(length(iris)-1)){
  nam <- paste0("p", i)
  x.label <- colnames(iris)[i]
  assign(nam, ggplot(iris, aes_string(x.label, fill = "Species")) + 
           geom_density(alpha = 0.3) + 
           xlab(x.label))
}
 
multiplot(p1, p2, p3, p4, cols = 2, title = "Multiplot function", 
          fontsize = 20, fontfamily = "Courier New")


multiplot with title

The function multiplot (adapted from source):

# 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.
#
multiplot <- function(..., plotlist = NULL, file, cols = 1, layout = NULL, title="", 
                      fontsize = 12, fontfamily = "Helvetica") {
  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 (nchar(title)>0){
    layout <- rbind(rep(0, ncol(layout)), layout)
  }
 
  if (numPlots==1) {
    print(plots[[1]])
 
  } else {
    # Set up the page
    grid.newpage()
    pushViewport(viewport(layout = grid.layout(nrow(layout), 
                          ncol(layout), 
                          heights = if (nchar(title)>0) {unit(c(0.5, rep(5,nrow(layout)-1)), "null")}
                          else {unit(c(rep(5, nrow(layout))), "null")})))
 
    # Make each plot, in the correct location
    if (nchar(title)>0) {
      grid.text(title, 
                vp = viewport(layout.pos.row = 1, layout.pos.col = 1:ncol(layout)),
                gp = gpar(fontsize = fontsize, fontfamily = fontfamily))
    }
 
    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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