R ggplot coord_cartesian(ylim()) vs ylim()

Former is limited to plot display only, while the latter is on the analysis result.

Let's use boxplot as an example.

require("ggplot2")

## Loading required package: ggplot2

## Warning: package 'ggplot2' was built under R version 3.0.3

df = data.frame(y = c(0, 50, 100, 501, 600))
median(df$y)

## [1] 100

p <- ggplot(df, aes(y = y)) + geom_boxplot(aes(x = factor(1)))

coord_cartesian(ylim) will

• analyze the entire dataset to produce the plot
• then, limit the plot to the range specified

p + coord_cartesian(ylim = c(0, 200))

ylim alone will

• limit the data set within the range
• then, analyze the leftover to produce the plot

p + ylim(c(0, 200))

## Warning: Removed 2 rows containing non-finite values (stat_boxplot).

as shown above,

• the warning tells you that 2 rows were left out, and
• the median with ylim alone is 50, rather 100.