!!!abline()
* 事前にplot()して、そこに線を引く
{{pre
x = c(1,2,3,4,5)
y = c(2,4,6,8,10)
plot(x, y, xlim=c(0,5), ylim=c(0,10))
abline(a=2, b=1) # a=切片, b=傾き
}}

{{pre
x = c(1,2,3,4,5)
y = c(2,4,6,8,10)
plot(x, y, xlim=c(0,5), ylim=c(0,10))
abline(lm(y ~ x)) # xとyの回帰式
}}

{{pre
x = c(1,2,3,4,5)
y = c(2,4,6,8,10)
plot(x, y, xlim=c(0,5), ylim=c(0,10))
abline(h=8)  # horizontal に
}}