r - combine two plots into one graph -

i trying draw pie charts r. how can combine following pie charts 1 graph?

data <- c(632,20,491,991,20) names <- c("alpha","beta","gamma","delta","omega") pie(data, names,col = c("red", "yellow", "blue", "green", "cyan"), main="pie chart 1")   data <- c(37376,41770,5210,5005,3947) names <- c("alpha","beta","gamma","delta","omega") pie(data, names,col = c("red", "yellow", "blue", "green", "cyan"), main="pie chart 2") 

par(mfrow=c(x,y)) # x number of rows , y columns. plot(...) plot(...) 

for more information regarding plotting multiple plots in 1 graphical window see: http://www.statmethods.net/advgraphs/layout.html