R ggplot - barplot

barplot

• load the package ggplot2 and the diamond data
• first we create a object p of class ggplot, where we map clarity to x (horizontal position)

p <- ggplot(diamonds, aes(x=clarity))
summary(p)

data: carat, cut, color, clarity, depth, table, price, x, y, z
  [53940x10]
mapping:  x = clarity
faceting: facet_grid(. ~ ., FALSE)

• p contains all information ggplot needs to build a barplot, all we have to do is adding a layer with geom="bar";

p + layer(geom="bar")

• to this simple barplot we can add the following (optional) aesthetics:
  • colour: color of the borders of the bins
  • fill: color of the filling
  • size:
  • linetype: line type of the borders
  • weight:
  • alpha: transparency of fill [0,1]

p + layer(geom="bar", geom_params=list(fill="steelblue", colour="black", linetype=4, alpha=0.3))

• but a barplot can visualize more information about the data - so we add a new mapping to p

p <- ggplot(diamonds, aes(x=clarity, fill=color)) # where color is the variable of the dataframe diamonds

• now the default output looks like:

p + layer(geom="bar")

• the plot can be customized by the same aesthetics, fill would override the aesthetic mapping of p
• additional we can add a position adjustment

p + layer(geom="bar", position="dodge") 

• or

p + layer(geom="bar", position="fill") 

• if we flip (coord_flip()) the underlying coordinate system, we can rotate the plot

p + layer(geom="bar", position="stack") + coord_flip()

• or we even can change the coordinate system to polar coordinates:

p + layer(geom="bar", position="stack") + coord_polar()