## illustrating the need for curly brackets (or not with for loops,
## functions, etc).  You don't need them if your function/loop/etc is
## only one line
n <- -5
for(i in 1:n)
  print(i^2)

## creating a matrix
matrix(1:18, nrow=4)

## creating a function with two arguments
my.sum <- function(a, b) {
  c <- a/b
  return(c)
}
## and applying that function to a range of values for one variable,
## but holding the other constant
sapply(1:10, my.sum, b=5)
sapply(1:10, my.sum, a=5)

## writing a figure straight to a pdf
pdf('~/Desktop/myplot.pdf', height=4, width=4)
par(oma=c(0.1,0.1,0.1,0.1), mar=c(3, 3, 0.1, 0.1), mgp=c(1,0.4,0))
plot(1:10, col='blue', pch=16, las=1)
dev.off()

## creating another matrix
m <- matrix(1:20, nrow=4)

## applying the "sum" function over rows vs columns (and, of course,
## you could also apply your own function)
apply(m, MARGIN=1, FUN=sum)
apply(m, MARGIN=2, FUN=sum)

## doing the same thing much less elegantly with an sapply
sapply(1:nrow(m), FUN=function(i) sum(m[i,]))
sapply(1:ncol(m), FUN=function(i) sum(m[,i]))

## creating a data-frame
dd <- data.frame(bird.mass=runif(20),
                 bird.age=sample(1:4, size=20, replace=TRUE),
                 bird.iq=sample(1:3, size=20, replace=TRUE))

## and then applying a function to that data-frame, using apply:
##
## e.g., if our equation was:
## bird.score = bird.mass + bird.age^bird.iq
eq7 <- function(a, b, c) a + b^c
dd$bird.score <-
  mapply(eq7, a=dd$bird.mass, b=dd$bird.age, c=dd$bird.iq)

## could also do this just directly, but this is not always possible
dd$bird.mass + dd$bird.age^dd$bird.iq