Question

R plots automatically set the x and y limits to put some space between the data and the axes. I was wondering if there is a way for matplotlib to do the same automatically. If not, is there a good formula or ‘rule of thumb’ for how R sets its axis limits?

Answer 1

Looking at ?par for the parameter xaxs:

The style of axis interval calculation to be used for the x-axis. Possible values are “r”, “i”, “e”, “s”, “d”. The styles are generally controlled by the range of data or xlim, if given.
Style “r” (regular) first extends the data range by 4 percent at each end and then finds an axis with pretty labels that fits within the extended range.

So if we try this out:

par(xaxs="r")       #The default  
plot(1:10, 1:10)

We can actually demonstrate that it’s +/- 4% of the range on each side:

abline(v=1-(diff(range(1:10)))*0.04, col="red")
abline(v=10+(diff(range(1:10)))*0.04, col="red")