拿R來畫畫（二）：毫無技巧的折線圖

繪製折線圖

• 觀察數據

head(pressure)

A data.frame: 6 × 2

temperature	pressure
<dbl>	<dbl>
0	0.0002
20	0.0012
40	0.0060
60	0.0300
80	0.0900
100	0.2700

• 基礎折線圖

plot(pressure$temperature, pressure$pressure, type="l")

• 點和線相結合

plot(pressure$temperature, pressure$pressure, type="l")
points(pressure$temperature, pressure$pressure)

• 一圖多線並設置不同的顏色屬性

plot(pressure$temperature, pressure$pressure, type="l")
points(pressure$temperature, pressure$pressure)
lines(pressure$temperature, pressure$pressure/2, col="red")
points(pressure$temperature, pressure$pressure/2, col="red")
lines(pressure$temperature, pressure$pressure/3, col="green")
points(pressure$temperature, pressure$pressure/3, col="blue")

• 和qplot的結果進行比對

library(ggplot2)
qplot(temperature, pressure, data=pressure, geom=c("line", "point"))
# 等價的寫法
# ggplot(pressure, aes(x=temperature, y=pressure)) + geom_line() + geom_point()