Multiple graphs over multiple pages using ggplot

Question

I am doing an exploratory analysis of my data and need to plot multiple graphics using ggplot. The amount of graphics is really huge (206 Stations), and I wanted to plot them in 1 column vs. 8 rows per page over the so many pages needed. I am aware of functions like viewport or grid.arrange, but I am not managing to make them work in this case. I have already noticed that layout() nor par(mfrow=c(8,1)) do not work with ggplot, but I send the part of the code where I am stuck bellow. Any help would be much appreciated!

pdf('test.pdf', width=21, height=27)
par(mfrow=c(8,1))
for(i in levels(tab$Station))
{

print(ggplot(tab[tab$Station==i], aes(x=Date)) +
  geom_line(aes(y=Tmin), col="blue", size=0.1) + 
  geom_line(aes(y=Tmax), col="red", size=0.1) + 
  geom_text(aes(x=as.Date('2010-01-01'), y=45), label=i) +
  ylim(0, 45) + 
  scale_x_date(labels = date_format("%Y")) +
  theme_bw() +
  theme(
    plot.background = element_blank()
    ,panel.grid.major = element_blank()
    ,panel.grid.minor = element_blank()
    ,panel.border = element_rect(color = 'black')
    ,panel.background = element_blank()

  )
)

}

dev.off()

Answer 1

Faceting might be the way to go. Decide how many faceted mini-plots you want per page, then loop through the required number of times, generating a png or a pdf as you go. So if you have 200 data items and you want 50 per page, in facets of 5 across and 10 down, just loop through 200/50 = 4 iterations. Crude, but should work.

library(ggplot2)

ii <- 7
nn <- 49

mydf <- data.frame(date = rep(seq(as.Date('2013-03-01'),
                       by = 'day', length.out = ii), nn),
                   value = rep(runif(nn, 100, 200)))

mydf$facet.variable <- rep(1:nn, each = ii)

p <- ggplot(mydf, aes(x = date, y = value)) +
    geom_line() +
    facet_wrap(~ facet.variable, ncol = ii)

print(p)

Answer 2

Unfortunately, mfrow doesn't work with ggplot2. You have to use other methods like this one or this one or use the native plot function.

Maybe you can use faceting to get the 8 plots onto one page, then the second link to put it into multiple documents...

Answer 3

You should simplify your plot since once you get the right order with a simple plot you just replace it with your complicated one. ggplot2 are based on grid package so you need to use gridExtra to arrange your plots. Then you loop through , for each 8 plots, you store them in a list and you call grid.arrange over it, and you repeat this until the end of your plots...

library(gridExtra)
library(ggplot2)
pdf('test.pdf', width=21, height=27)
i = 1
plot = list() 
for (n in unique(tab$Station)){
  ### process data for plotting here ####
  plot[[i]] = ggplot(tab[tab$Station==n], aes(x=Date)) +...
  if (i %% 8 == 0) { ## print 8 plots on a page
    print (do.call(grid.arrange,  plot))
    plot = list() # reset plot 
    i = 0 # reset index
  }
  i = i + 1
}
if (length(plot) != 0) { 
  print (do.call(grid.arrange,  plot))
}
dev.off()

Answer 4

library(plyr)
library(gridExtra)

p = ggplot(tab, aes(x=Date)) +
       geom_line(aes(y=Tmin), col="blue", size=0.1)

plots = dlply(tab , "Station", `%+%`, e1 = p)
ml = do.call(marrangeGrob, c(plots, list(nrow=8, ncol=1)))
ggsave("multipage.pdf", ml)

untested.