我怎样才能把一个转换的比例放在ggplot2的右边？ [英] How can I put a transformed scale on the right side of a ggplot2?

问题描述

我正在创建一个图表，显示随着时间的推移湖面水平的变化。我附上了一个简单的例子。我想在图表的右侧添加一个刻度（刻度线和注释），用于显示以英尺为单位的标高。我知道ggplot2不会允许两个不同的比例（请参阅用2个y轴绘制，一个y轴在左边，另一个y轴在右边），但是因为这是相同的规模，有没有办法做到这一点？我宁愿继续使用ggplot2，也不必恢复到plot（）函数。

I'm creating a graph showing the change in lake levels over time. I've attached a simple example below. I would like to add a scale (tick marks and annotation) on the right side of the plot that shows the elevation in feet. I know ggplot2 won't allow two different scales (see Plot with 2 y axes, one y axis on the left, and another y axis on the right), but because this is a transformation of the same scale, is there a way to do this? I'd prefer to keep using ggplot2 and not to have to revert to the plot() function.

library(ggplot2)
LakeLevels<-data.frame(Day=c(1:365),Elevation=sin(seq(0,2*pi,2*pi/364))*10+100)
p <- ggplot(data=LakeLevels) + geom_line(aes(x=Day,y=Elevation)) + 
  scale_y_continuous(name="Elevation (m)",limits=c(75,125)) 
p

推荐答案

你应该看看这个链接 http://rpubs.com/kohske/dual_axis_in_ggplot2 。

I已经调整了您的示例中提供的代码。这个修复看起来很黑客，但它让你成为那里的一部分。剩下的唯一部分就是搞清楚如何在图的右边添加文本。

I've adapted the code provided there for your example. This fix seems very "hacky", but it gets you part of the way there. The only piece left is figuring out how to add text to the right axis of the graph.

    library(ggplot2)
    library(gtable)
    library(grid)
    LakeLevels<-data.frame(Day=c(1:365),Elevation=sin(seq(0,2*pi,2*pi/364))*10+100)
    p1 <- ggplot(data=LakeLevels) + geom_line(aes(x=Day,y=Elevation)) + 
          scale_y_continuous(name="Elevation (m)",limits=c(75,125))

    p2<-ggplot(data=LakeLevels)+geom_line(aes(x=Day, y=Elevation))+
        scale_y_continuous(name="Elevation (ft)", limits=c(75,125),           
        breaks=c(80,90,100,110,120),
                 labels=c("262", "295", "328", "361", "394"))

    #extract gtable
    g1<-ggplot_gtable(ggplot_build(p1))
    g2<-ggplot_gtable(ggplot_build(p2))

    #overlap the panel of the 2nd plot on that of the 1st plot

    pp<-c(subset(g1$layout, name=="panel", se=t:r))
    g<-gtable_add_grob(g1, g2$grobs[[which(g2$layout$name=="panel")]], pp$t, pp$l, pp$b, 
                       pp$l)

   ia <- which(g2$layout$name == "axis-l")
   ga <- g2$grobs[[ia]]
   ax <- ga$children[[2]]
   ax$widths <- rev(ax$widths)
   ax$grobs <- rev(ax$grobs)
   ax$grobs[[1]]$x <- ax$grobs[[1]]$x - unit(1, "npc") + unit(0.15, "cm")
   g <- gtable_add_cols(g, g2$widths[g2$layout[ia, ]$l], length(g$widths) - 1)
   g <- gtable_add_grob(g, ax, pp$t, length(g$widths) - 1, pp$b)

   # draw it
   grid.draw(g)

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