RGraphGallery

• sometimes it is useful to transform the values
• in ggplot you have the choice between transforming the values or the axis
• here is an example to compare both
• the data set movie is part of the ggplot package, additional used are the gridExtra package (grid.arrange), the scales package (labels formatter "dollar")
• in the beginning a cut the year var in 15 even spaced intervals
• on the lefthandside is the plot with the transformation of the axis, on the righthandside with transformation of values

movies$years <- cut(movies$year,breaks=15)

p <- ggplot(movies, aes(x=years,y=budget,colour=years)) +
## bar filling
  geom_boxplot(fill="black") + 
## add mean points
  stat_summary(fun.y="mean",geom="point") + 
 ## customize tick labels
  opts(axis.text.x = theme_text(angle=270,hjust=0,vjust=1)) +
## get rid of the legend
  opts(legend.position="none") 

## log transformation of the y axis
p1 <- p + scale_y_continuous(labels=dollar,trans="log")

## compare with
## here we do the transformation while mapping:
p2 <- ggplot(movies, aes(x=years,y=log(budget),colour=years)) +
  geom_boxplot(fill="black") +
  stat_summary(fun.y="mean",geom="point") +
  opts(axis.text.x = theme_text(angle=270,hjust=0,vjust=1)) +
  opts(legend.position="none")

## plot both graphs on one page
grid.arrange(p1,p2,ncol=2)