Question

I want to create a big plot which contains four subplots made by plot() function.
All the subplots are saved as png/pdf file format.
Is there way in R to import these plots to R then create a big plot that contains all the subplots?

Answer 1

Would it not be easier to fix the problem at source by creating each plot, laying them out together then saving them as one file? The grid layout functions should work with the base plot function as far as I can tell. Here’s a simple example using ggplot2. If you use ggplot you could perhaps also use the facet functions. Code follows after image.

library(ggplot2)
library(grid)

set.seed(23456)
mydf <- data.frame(mydate = seq(as.Date('2012-01-01'), as.Date('2012-12-01'), by = '1 month'),
                   run1 = runif(12, 100, 200),
                   run2 = runif(12, 300, 400),
                   run3 = runif(12, 1000, 2000),
                   run4 = runif(12, 2000, 3000))

p1 <- ggplot(data = mydf) +
         geom_line(aes(x = mydate, y = run1))

p2 <- ggplot(data = mydf) +
         geom_line(aes(x = mydate, y = run2))

p3 <- ggplot(data = mydf) +
         geom_line(aes(x = mydate, y = run3))

p4 <- ggplot(data = mydf) +
         geom_line(aes(x = mydate, y = run4))


png(filename = paste("multipleplot.png", sep = ""), width = 600, height = 600, units = "px", res = NA)
grid.newpage()
pushViewport(viewport(layout = grid.layout(2, 2, widths = c(300, 300))))

vplayout <- function(x, y)
    viewport(layout.pos.row = x, layout.pos.col = y)

print(p1, vp = vplayout(1,1))
print(p2, vp = vplayout(1,2))
print(p3, vp = vplayout(2,1))
print(p4, vp = vplayout(2,2))
dev.off()