Simple example of transforming data/scale/coordinate system in ggplot2.

Transformations

library(ggplot2)

# Sample diamonds dataframe:
didat <- diamonds[sample(nrow(diamonds), 1000), ]

# Original data:
ggplot(didat, aes(x = depth, y = price)) + geom_point()

# Transform data:
ggplot(didat, aes(x = log10(depth), y = log10(price))) + geom_point()

# Transform scales (same plot visually as transform data, but scales go wonky):
ggplot(didat, aes(x = depth, y = price)) + geom_point() +
  scale_x_log10() + scale_y_log10()

# Transform coordinate system:
ggplot(didat, aes(x = depth, y = price)) + geom_point() +
  coord_trans(x = "log10", y = "log10")

Visual summary provided at http://rpubs.com/mattsigal/ggtransforms