I am using ggplot2 to make several area plots of time series. To my eye, the plots look better if the time series covers the entire x axis, the height of the highest area is about 5% - 10% below the top of the plot area, and the legend is situated in the lower right corner of the plot.
Let base.plot be a base plot that labels the x axis and formats its tick marks, adds NBER recession bars, and locates the legend in the lower right corner of the plot itself with:
base.plot <- base.plot + theme(
legend.justification = c(1,0),
legend.position = c(1,0),
legend.title = element_blank()
)
This seems to work fine with my line plots, but on the area plots the legend box sticks out to the right and below the plot itself. Instead, its lower right corner should be at the lower right corner of the plot area. How can I fix this?
To change the plot's extent relative to its axes, I tried using the expand argument to expand the plot horizontally and vertically. Documentation for this argument leaves something to be desired, to say the least:
expand
A numeric vector of length two giving multiplicative and additive expansion constants. These constants ensure that the data is placed some distance away from the axes. The defaults are c(0.05, 0) for continuous variables, and c(0, 0.6) for discrete variables.
Is it too much to ask for the formula so we can know what the multiplicative and additive constants actually do? Otherwise, how else can we know how to set them? The above description appears in the documentation for scale_x_date; is it too much to ask for some mention of the defaults for date variables?
Flying blind, thanks to the useless documentation, I tried the solution for continuous variables:
scale_x_date(expand = c(0,0)),
But this just scrunched up the plot towards the right of the chart. So where can I learn about using scale_x_date with the expand argument?
As for the vertical axis, scale_y_date(expand = c(0,0)) did bring the bottom of the area plots down to the x-axis. But the top is too high. Somewhere I saw that a modification to the scale_y_date code now allows four arguments, two for the lower bound and two for the upper one. I tried this too, but there's no discernible difference from the plot using only the two parameters.
So, how can I get the lowest area plot to sit on the x axis and the highest point to be about 0.5 in from the top?
