Say I plot the following in R:
carrots <- data.frame(length = rnorm(500000, 10000, 10000))
cukes <- data.frame(length = rnorm(50000, 10000, 20000))
carrots$veg <- 'carrot'
cukes$veg <- 'cuke'
vegLengths <- rbind(carrots, cukes)
ggplot(vegLengths, aes(length, fill = veg)) + geom_density(alpha = 0.2)
Basically you have two options
scale_x_continuous(limits = c(-5000, 5000))
coord_cartesian(xlim = c(-5000, 5000))
Where the first removes all data points outside the given range and the second only adjusts the visible area. In most cases you would not see the difference, but if you fit anything to the data it would probably change the fitted values.
You can also use the shorthand function
ylim), which like the first option removes data points outside of the given range:
+ xlim(-5000, 5000)
For more information check the description of