One R Tip A Day uses a custom R function to plot two or more overlapping density plots on the same graph.
The same can be very easily accomplished in ggplot2.
> library(ggplot2) |
Create dummy dataframe:
> df <- data.frame(x = rnorm(1000, 0, 1), y = rnorm(1000,
0, 2), z = rnorm(1000, 2, 1.5))
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“Melt” data:
> df.m <- melt(df) |
Default plot:
> ggplot(df.m) + geom_freqpoly(aes(x = value,
y = ..density.., colour = variable))
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Default plot + few formatting adjustments:
> ggplot(df.m) + geom_freqpoly(aes(x = value,
y = ..density.., colour = variable)) +
labs(x = NULL) + opts(legend.position = "none") +
opts(title = "Frequency Polygons (based on binned counts)")
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Update: Hadley kindly points out that the above plots are frequency polygons. I have updated the post with a “real” density plot.
> ggplot(df.m) + geom_density(aes(x = value,
colour = variable)) + labs(x = NULL) +
opts(legend.position = "none") + opts(title = "Densities from a kernel density estimator")
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