Question

我正在创建一个图表，显示湖水位随时间的变化。我在下面附上了一个简单的例子。我想在图的右侧添加一个刻度（刻度线和注释），以英尺为单位显示高程。我知道ggplot2不会允许两个不同的比例（见Plot with 2 y axes, one y axis on the left, and another y axis on the right），但因为这是相同比例的转换，有没有办法做到这一点？我更喜欢继续使用ggplot2而不必恢复到plot（）函数。

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

Answer 1

您应该查看此链接http://rpubs.com/kohske/dual_axis_in_ggplot2。

我已根据您的示例调整了此处提供的代码。这个修复看起来非常“hacky”，但它会让你成为那里的一部分。剩下的唯一一点是弄清楚如何将文本添加到图表的右轴。

    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)

enter image description here

Answer 2

我可能已经找到了一个放置轴标题的解决方案，其中一些来自Nate Pope答案的想法可以在这里找到：
ggplot2: Adding secondary transformed x-axis on top of plot
关于在gtable中访问grobs的讨论： https://groups.google.com/forum/m/#!topic/ggplot2-dev/AVHHcYqc5uU

最后，我刚刚添加了一行

g <- gtable_add_grob(g, g2$grob[[7]], pp$t, length(g$widths), pp$b)

在致电grid.draw(g)之前，这似乎可以解决问题据我了解，它采用y轴标题g2$grob[[7]]并将其置于最右侧。它可能不是美妙的解决方案，但它对我有用。

最后一件事。找到一种旋转轴标题的方法会很好。

此致

添

Answer 3

这个问题已得到解答，但是在ggplot对象的右侧添加辅助轴和辅助比例的一般问题是一直出现的问题。我想在下面报告我对问题的调整，基于此线程中的各种答案给出的几个元素以及其他几个线程（参见下面的部分参考列表）。

我需要批量生产双y轴图，所以我构建了一个函数ggplot_dual_axis()。以下是潜在兴趣的特征：

代码显示y轴和y轴的网格线（这是我的主要贡献，尽管它很简单）
代码打印欧元符号并将其嵌入pdf （我在那里看到的内容：Plotting Euro Symbol € in ggplot2?）
代码试图避免两次打印某些元素（“尝试”表示我怀疑它是否完全成功）

未回答的问题：

有没有办法修改ggplot_dual_axis()函数以删除其中一个geom_line()或geom_point()或其他任何内容，如果不存在此类geom元素则不会抛出错误。在伪代码中类似于if has(geom_line) ...
如何通过关键字而不是索引来调用g2$grobs[[7]]？这就是它返回的内容：text[axis.title.y.text.232]我对这个问题的兴趣源于我通过应用类似的技巧尝试抓住网格线的失败。我认为网格线隐藏在g2$grobs[[4]]内的某处，但我不确定如何访问它们。

修改即可。问题我能够自己回答：如何增加右侧的情节余量，其中“欧元”标签是？答案：例如，theme(plot.margin = unit(c(1,3,0.5,0.8), "lines"))可以解决问题。

请指出任何明显的问题或建议改进。

现在代码：希望它对某人有用。正如我所说，我并不主张原创性，这是其他人已经表现出的事物的组合。

##' function named ggplot_dual_axis()
##' Takes 2 ggplot plots and makes a dual y-axis plot
##' function takes 2 compulsory arguments and 1 optional argument
##' arg lhs is the ggplot whose y-axis is to be displayed on the left
##' arg rhs is the ggplot whose y-axis is to be displayed on the right
##' arg 'axis.title.y.rhs' takes value "rotate" to rotate right y-axis label
##' The function does as little as possible, namely:
##'  # display the lhs plot without minor grid lines and with a
##'  transparent background to allow grid lines to show
##'  # display the rhs plot without minor grid lines and with a
##'  secondary y axis, a rotated axis label, without minor grid lines
##'  # justify the y-axis label by setting 'hjust = 0' in 'axis.text.y'
##'  # rotate the right plot 'axis.title.y' by 270 degrees, for symmetry
##'  # rotation can be turned off with 'axis.title.y.rhs' option
##'  

ggplot_dual_axis <- function(lhs, rhs, axis.title.y.rhs = "rotate") {
  # 1. Fix the right y-axis label justification
    rhs <- rhs + theme(axis.text.y = element_text(hjust = 0))
  # 2. Rotate the right y-axis label by 270 degrees by default
    if (missing(axis.title.y.rhs) | 
        axis.title.y.rhs %in% c("rotate", "rotated")) {
        rhs <- rhs + theme(axis.title.y = element_text(angle = 270)) 
    }
  # 3a. Use only major grid lines for the left axis
    lhs <- lhs + theme(panel.grid.minor = element_blank())
  # 3b. Use only major grid lines for the right axis
  #     force transparency of the backgrounds to allow grid lines to show
    rhs <- rhs + theme(panel.grid.minor = element_blank(), 
        panel.background = element_rect(fill = "transparent", colour = NA), 
        plot.background = element_rect(fill = "transparent", colour = NA))
# Process gtable objects
  # 4. Extract gtable
    library("gtable") # loads the grid package
    g1 <- ggplot_gtable(ggplot_build(lhs))
    g2 <- ggplot_gtable(ggplot_build(rhs))
  # 5. Overlap the panel of the rhs plot on that of the lhs 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)
  # Tweak axis position and labels
    ia <- which(g2$layout$name == "axis-l")
    ga <- g2$grobs[[ia]]
    ax <- ga$children[["axis"]]  # 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)
    g <- gtable_add_grob(g, g2$grobs[[7]], pp$t, length(g$widths), pp$b)
  # Display plot with arrangeGrob wrapper arrangeGrob(g)
    library("gridExtra")
    grid.newpage()
    return(arrangeGrob(g))
}

低于一些假数据和两个以美元和欧元为单位的情节。如果有一个包可以让你制作一个图并且用它来包围调用双y轴图（例如ggplot_dual_axis_er(ggplot_object, currency = c("dollar", "euro"))）它会不会很酷并且会自动为你获取汇率！： - ）

# Set directory:
if(.Platform$OS.type == "windows"){
  setwd("c:/R/plots")
} else { 
  setwd("~/R/plots")
}

# Load libraries
library("ggplot2")
library("scales")

# Create euro currency symbol in plot labels, simple version
# avoids loading multiple libraries
# avoids problems with rounding of small numbers, e.g. .0001
labels_euro <- function(x) {# no rounding
paste0("€", format(x, big.mark = ",", decimal.mark = ".", trim = TRUE,
    scientific = FALSE))
} 

labels_dollar <- function(x) {# no rounding: overwrites dollar() of library scales
paste0("$", format(x, big.mark = ",", decimal.mark = ".", trim = TRUE,
    scientific = FALSE))
} 

# Create data
df <- data.frame(
  Year = as.Date(c("2001", "2002", "2003", "2004", "2005", "2006", "2007", "2008", "2009", "2010", "2011", "2012", "2013", "2014", "2015", "2016", "2017", "2018"),
    "%Y"), 
  Dollar = c(0, 9000000, 1000000, 8000000, 2000000, 7000000, 3000000, 6000000, 4000000, 5000000, 5000000, 6000000, 4000000, 7000000, 300000, 8000000, 2000000, 9000000))
# set Euro/Dollar exchange rate at 0.8 euros = 1 dollar
df <- cbind(df, Euro = 0.8 * df$Dollar)
# Left y-axis
p1 <- ggplot(data = df, aes(x = Year, y = Dollar)) + 
    geom_line(linestyle = "blank") + # manually remove the line
    theme_bw(20) +                   # make sure font sizes match in both plots
    scale_x_date(labels = date_format("%Y"), breaks = date_breaks("2 years")) + 
    scale_y_continuous(labels = labels_dollar, 
        breaks = seq(from = 0, to = 8000000, by = 2000000))
# Right y-axis
p2 <- ggplot(data = df, aes(x = Year, y = Euro)) + 
    geom_line(color = "blue", linestyle = "dotted", size = 1) + 
    xlab(NULL) +                     # manually remove the label
    theme_bw(20) +                   # make sure font sizes match in both plots
    scale_x_date(labels = date_format("%Y"), breaks = date_breaks("2 years")) +
    scale_y_continuous(labels = labels_euro, 
        breaks = seq(from = 0, to = 7000000, by = 2000000))

# Combine left y-axis with right y-axis
p <- ggplot_dual_axis(lhs = p1, rhs = p2)
p

# Save to PDF
pdf("ggplot-dual-axis-function-test.pdf", 
  encoding = "ISOLatin9.enc", width = 12, height = 8)
p
dev.off()

embedFonts(file = "ggplot-dual-axis-function-test.pdf", 
           outfile = "ggplot-dual-axis-function-test-embedded.pdf")

enter image description here

部分参考文献清单：

Answer 4

为了旋转轴标题，请将以下内容添加到p2图表中：

p2 <- p2 + theme(axis.title.y=element_text(angle=270))

如何在ggplot2的右侧放置转换后的比例？

4 个答案: