我有一个包含不同变量和不同单位的时间序列,我想显示在同一个图上.
ggplot不支持多轴(as explained here),因此我遵循建议,try 使用面绘制曲线:
x <- seq(0, 10, by = 0.1)
y1 <- sin(x)
y2 <- sin(x + pi/4)
y3 <- cos(x)
my.df <- data.frame(time = x, currentA = y1, currentB = y2, voltage = y3)
my.df <- melt(my.df, id.vars = "time")
my.df$Unit <- as.factor(rep(c("A", "A", "V"), each = length(x)))
ggplot(my.df, aes(x = time, y = value)) + geom_line(aes(color = variable)) + facet_wrap(~Unit, scales = "free_y", nrow = 2)
结果如下:
问题是只有一个y标签,上面写着"值",我想要两个:一个是"电流(A)",另一个是"电压(V)".
这可能吗?