[R] How do I move the horizontal axis in a plot so that it starts at the zero of the vertical axis?

[andrejfavia at ml1.net]

Alright but then if I include an aspect ratio, the y-axis no longer
starts at 0 at the bottom of the plot.

x <- c(-2.5, -1.3, 0.6, 0.8, 2.1)
y <- c(0.3, 1.9, 1.4, 0.7, 1.1)

plot(x, y, ylim=c(0, 2), yaxs="i", asp=1.25)