Arrange many plots using gridExtra

Question

I have spent many hours trying to fit 11 graphs in one plot and arrange them using gridExtra but I have failed miserably, so I turn to you hoping you can help.

Answer 1

I had to change the qplot loop call slightly (i.e. put the factors in the data frame) as it was throwing a mismatched size error. I'm not including that bit since that part is obviously working in your environment or it was an errant paste.

Try adjusting your widths units like this:

widths=unit(c(1000,50),"pt")

And you'll get something a bit closer to what you were probably expecting:

And, I can paste code now a few months later :-)

library(ggplot2)
library(gridExtra)

df <- data.frame(price=matrix(sample(1:1000, 100, replace = TRUE), ncol = 1))

df$size1 = 1:nrow(df)
df$size1 = cut(df$size1, breaks=11)
df=df[sample(nrow(df)),]
df$size2 = 1:nrow(df)
df$size2 = cut(df$size2, breaks=11)
df=df[sample(nrow(df)),]
df$clarity = 1:nrow(df)
df$clarity = cut(df$clarity, breaks=6)

# Create one graph for each size1, plotting the median price vs. the size2 by clarity:
for (c in 1:length(table(df$size1))) {

  mydf = df[df$size1==names(table(df$size1))[c],]
  mydf = aggregate(mydf$price, by=list(mydf$size2, mydf$clarity),median);   
  names(mydf)[1] = 'size2'
  names(mydf)[2] = 'clarity'
  names(mydf)[3] = 'median_price'
  mydf$clarity <- factor(mydf$clarity)

  assign(paste("p", c, sep=""), 
         qplot(data=mydf, 
               x=as.numeric(size2), 
               y=median_price, 
               group=clarity, 
               geom="line", colour=clarity, 
               xlab = "number of samples", 
               ylab = "median price", 
               main = paste("region number is ",c, sep=''), 
               plot.title=element_text(size=10)) + 
           scale_colour_discrete(name = "clarity") + 
           theme_bw() + theme(axis.title.x=element_text(size = rel(0.8)), 
                              axis.title.y=element_text(size = rel(0.8)), 
                              axis.text.x=element_text(size=8),
                              axis.text.y=element_text(size=8) ))
}

# Use gridExtra to arrange the 11 plots:

g_legend<-function(a.gplot){
  tmp <- ggplot_gtable(ggplot_build(a.gplot))
  leg <- which(sapply(tmp$grobs, function(x) x$name) == "guide-box")
  legend <- tmp$grobs[[leg]]
  return(legend)}

mylegend<-g_legend(p1)


grid.arrange(arrangeGrob(p1 + theme(legend.position="none"),
                         p2 + theme(legend.position="none"),
                         p3 + theme(legend.position="none"),
                         p4 + theme(legend.position="none"),
                         p5 + theme(legend.position="none"),
                         p6 + theme(legend.position="none"),
                         p7 + theme(legend.position="none"),
                         p8 + theme(legend.position="none"),
                         p9 + theme(legend.position="none"),
                         p10 + theme(legend.position="none"),
                         p11 + theme(legend.position="none"),
                         top ="Main title",
                         left = ""), mylegend, 
             widths=unit(c(1000,50),"pt"), nrow=1)

Edit (16/07/2015): with gridExtra >= 2.0.0, the main parameter has been renamed top.