Learn ggplot2 by example. This tutorial is especially useful and easy to follow if you went through Hadley Wickham's article on the Layered Grammar of Graphics. https://www.dropbox.com/s/enzoi6b5yfwpvhm/layered-grammar.pdf

ggplot2-demo.R

library(ggplot2)

# Take a look at our example dataset  
head(diamonds)

# Make a chart from scratch
x = ggplot() +
  layer(
    data = diamonds, mapping = aes(x=carat,y=price),
    stat='identity', position="identity", geom="point"
  ) +
  scale_x_continuous() +
  scale_y_continuous() +
  coord_cartesian()
x 
#TODO: Convert this into a jitter plot
ggplot() +
  layer(
    data = diamonds, mapping = aes(x=carat,y=price),
    stat='identity', position="jitter", geom="point"
  ) +
  scale_x_continuous() +
  scale_y_continuous() +
  coord_cartesian()

# Adding a regression layer
y = x + layer(
  data = diamonds, mapping = aes(x=carat,y=price),
  stat='smooth', position="identity", geom="smooth"
 )
y

# TODO: Is this a power curve?
# add 1. y <- ..., and x and y log scale
y + scale_x_log10() + scale_y_log10()

# IDENTITITY TRANSFORMATIONS
# Build up the same with defaults, as follows:
# 1. Get rid of stat and position
# 2. Get rid of scales and coordinates
# All of these are good by default

ggplot() +
  layer(
    data = diamonds, mapping = aes(x=carat,y=price),
    geom="point"
  ) + 
layer(
  data = diamonds, mapping = aes(x=carat,y=price),
  geom="smooth"
)

# 3. get rid of layer definitintions
ggplot(data = diamonds, mapping = aes(x=carat,y=price)) +
  geom_point() + geom_smooth()

# 4. switch to qplot 
qplot(carat,price,data=diamonds,geom=c('point','smooth'))

# 5. log='xy'
qplot(carat,price,data=diamonds,geom=c('point','smooth'),log='xy')

# 6. Let's change the theme to bw
qplot(carat,price,data=diamonds,geom=c('point','smooth'),log='xy') +
  theme_bw()

# A FEW EXTRA FEATURES

# TODO: Faceting
qplot(carat,price,data=diamonds,geom=c('point','smooth'),log='xy') + facet_grid(. ~ cut)

# TODO: Histogram by cut 
qplot(cut,data=diamonds)

# TODO: Histogram as barchart
ggplot(diamonds,aes(x="",fill=cut)) + geom_bar(width=1)

# TODO: Pie Chart
ggplot(diamonds,aes(x="",fill=cut)) + geom_bar(width=1) + coord_polar(theta='y')