GGplot - Stat - (Statistical transformation|Statistic)

About

The Statistical transformation (stat). Multiple layers, statistical transformation.

It's often useful to transform your data before plotting, and that's what statistical transformations do.

Stat, geom relation

Every geom function has a default statistic:

And every statistic function has a default geom.

  • stat_…

List of statistic

Some statistics produce new data frame variables in the data. stat_bin produces count and density.

Management

Mapping a new stat to an aesthetic

Some statistics produce new data frame variables in the data.

Example: stat_bin produces count and density.

To map an aesthetic to one of the new stat variables, surround it with ..

p = ggplot(diamonds, aes(x=price))
p + geom_histogram(aes(y = ..density..))
p + geom_histogram(aes(colour = ..count..))

Separation of statistics and geometric elements

Ggplot - Geom (geometric objects) - type of plot

p <- ggplot(diamonds, aes(x=price))
p + stat_bin(geom="bar") # Equivalent to p + geom_histogram()
p + stat_bin(geom="area")
p + stat_bin(geom="point")
p + stat_bin(geom="line")

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