You want to use lines
to add the second line, meanwhile making sure that ylim
allows for all the values being plotted to fit within the plotting region.
plot(y1 ~ x, ylim = range(c(y1, y2)), xlab = "x label", ylab = "y label",
main = "This one might work!", type = 'b', pch = 19, col = "orchid")
lines(y2, type = 'b', pch = 19, col = 'slateblue')
legend("topright", c("R is", "awesome"), col = c("orchid","slateblue"), pch = 19)