Combined plot of ggplot2 (Not in a single Plot), using par() or layout() function?

Question

I've been thinking of using par() or layout() functions for combining ggplots. Will it be possible to use those functions?

Say I want to plot ggplot for scatterplot and ggplot for histogram. And I want to combine the two plots (NOT IN A SINGLE PLOT). Is it applicable?

I tried it with simple plotting in R, without using the ggplot functions. And it works actually.

Here's a sample from Quick-R, Link: http://www.statmethods.net/advgraphs/layout.html

# 4 figures arranged in 2 rows and 2 columns
attach(mtcars)
par(mfrow=c(2,2))
plot(wt,mpg, main="Scatterplot of wt vs. mpg")
plot(wt,disp, main="Scatterplot of wt vs disp")
hist(wt, main="Histogram of wt")
boxplot(wt, main="Boxplot of wt")

# One figure in row 1 and two figures in row 2
attach(mtcars)
layout(matrix(c(1,1,2,3), 2, 2, byrow = TRUE))
hist(wt)
hist(mpg)
hist(disp)

But when I try to use ggplot, and combine the plot, I don't get an output.

Answer 1

library(ggplot2)
library(grid)


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


plot1 <- qplot(mtcars,x=wt,y=mpg,geom="point",main="Scatterplot of wt vs. mpg")
plot2 <- qplot(mtcars,x=wt,y=disp,geom="point",main="Scatterplot of wt vs disp")
plot3 <- qplot(wt,data=mtcars)
plot4 <- qplot(wt,mpg,data=mtcars,geom="boxplot")
plot5 <- qplot(wt,data=mtcars)
plot6 <- qplot(mpg,data=mtcars)
plot7 <- qplot(disp,data=mtcars)

# 4 figures arranged in 2 rows and 2 columns
grid.newpage()
pushViewport(viewport(layout = grid.layout(2, 2)))
print(plot1, vp = vplayout(1, 1))
print(plot2, vp = vplayout(1, 2))
print(plot3, vp = vplayout(2, 1))
print(plot4, vp = vplayout(2, 2))


# One figure in row 1 and two figures in row 2
grid.newpage()
pushViewport(viewport(layout = grid.layout(2, 2)))
print(plot5, vp = vplayout(1, 1:2))
print(plot6, vp = vplayout(2, 1))
print(plot7, vp = vplayout(2, 2))