Axes - R Graphics - page 254

See Also
For more on controlling the scaling ratio of the x- and y-axes, see Setting the Scaling Ratio of
the X- and Y-Axes .

Making a Circular Graph

Problem
You want to make a circular graph.

Solution
Use coord_polar() . For this example we'll use the wind data set from gcookbook . It contains
samples of wind speed and direction for every 5 minutes throughout a day. The direction of the
wind is categorized into 15-degree bins, and the speed is categorized into 5 m/s increments:

library(gcookbook) # For the data set
wind

TimeUTC Temp WindAvg WindMax WindDir SpeedCat DirCat
0 3.54 9.52 10.39 89 10 - 15 90

5 3.52 9.10 9.90 92 5 - 10 90

10 3.53 8.73 9.51 92 5 - 10 90

...
2335 6.74 18.98 23.81 250 > 20 255

2340 6.62 17.68 22.05 252 > 20 255

2345 6.22 18.54 23.91 259 > 20 255

We'll plot a count of the number of samples at each SpeedCat and DirCat using
geom_histogram() ( Figure 8-33 ). We'll set binwidth to 15 and make the origin of the his-
togram start at -7.5, so that each bin is centered around 0, 15, 30, etc.:

ggplot(wind, aes(x = DirCat, fill = SpeedCat)) +
geom_histogram(binwidth = 15 , origin = -7.5 ) +
coord_polar() +
scale_x_continuous(limits = c( 0 , 360 ))