使用 ggplot 包 R 更改图中 yaxis 面的标签

这是我的数据集和生成绘图的代码。

library(reshape)
library(ggplot2)
set.seed(357)
myLetters <- function(length.out) {
a <- rep(letters, length.out = length.out)
grp <- cumsum(a == "a")
vapply(seq_along(a), 
     function(x) paste(rep(a[x], grp[x]), collapse = ""),
     character(1L))
}
name <- myLetters(90)
x <- data.frame(name = name, before = runif(90,min=-1, max=1),after =    runif(90,min=-0.2, max=0.2))
x <- x[order(x$before),]
xnew <- melt(x, id="name")
adata <- subset(xnew,xnew$variable=="after")
adata$name1 <- rep(1:90)
bdata <- subset(xnew,xnew$variable=="before")
bdata$name1 <- rep(1:90)
d <- rbind(bdata,adata)
d$name1 <- factor(d$name1,levels =c(1:90),labels = bdata$name)
colorname <- c("dark blue","dark red")
plot <- ggplot(data=d,aes(x=value,y=name1,group=variable,color=variable))+
    scale_fill_manual(values=colorname) +  
    scale_colour_manual(values=colorname) +  # I ADDED THIS LINE
    geom_point(size=1)+
    geom_path(aes(linetype = variable),size=0.3)+
    scale_linetype_manual(values=c("dashed", "solid"))+
    geom_vline(xintercept = c(-0.5,0,0.5),color="purple",size=0.5)+
   theme(panel.border = element_rect(colour = "black", fill=NA, size=0.5)
   )

plot

由于有 90 个标签，因此 y 轴刻度线标签彼此太接近。有没有办法定位 y 轴刻度线标签，以便第一个标签位于默认位置，第二个标签反映在 y 轴上，依此类推，对于所有 90 个标签？也许这有助于使情节更容易阅读。

我认为没有任何方法可以使用常规方法来做到这一点ggplot2命令。但可以使用编辑情节grid编辑功能。两种可能性：第一种使 y 轴标签交错，如图所示here https://stackoverflow.com/questions/36985825/stagger-axis-labels-new-feature-in-ggplot2/38024936#38024936;正如您所建议的，第二个是反映 y 轴上的每个第二个标签（和刻度线）。我让你来决定是否比原版更具可读性。

## Your data and code to generate the unedited plot

library(reshape)
library(ggplot2)
library(grid)
set.seed(357)
myLetters <- function(length.out) {
a <- rep(letters, length.out = length.out)
grp <- cumsum(a == "a")
vapply(seq_along(a), 
     function(x) paste(rep(a[x], grp[x]), collapse = ""),
     character(1L))
}
name <- myLetters(90)
x <- data.frame(name = name, before = runif(90,min=-1, max=1),after =    runif(90,min=-0.2, max=0.2))
x <- x[order(x$before),]
xnew <- melt(x, id="name")
adata <- subset(xnew,xnew$variable=="after")
adata$name1 <- rep(1:90)
bdata <- subset(xnew,xnew$variable=="before")
bdata$name1 <- rep(1:90)
d <- rbind(bdata,adata)
d$name1 <- factor(d$name1,levels =c(1:90),labels = bdata$name)
colorname <- c("dark blue","dark red")
plot <- ggplot(data=d,aes(x=value,y=name1,group=variable,color=variable))+
    scale_fill_manual(values=colorname) +  
    scale_colour_manual(values=colorname) +  # I ADDED THIS LINE
    geom_point(size=1)+
    geom_path(aes(linetype = variable),size=0.3)+
    scale_linetype_manual(values=c("dashed", "solid"))+
    geom_vline(xintercept = c(-0.5,0,0.5),color="purple",size=0.5)+
   theme(panel.border = element_rect(colour = "black", fill=NA, size=0.5)
   ) + theme_bw()

plot

第一种可能性

# Get the ggplot grob
g = ggplotGrob(plot)

# Make the relevant column a little wider
g$widths[3] = unit(1.5, "cm")

# Get a hierarchical list of component grobs
grid.ls(grid.force(g)) 

浏览列表以找到涉及左轴的部分。相关位是：

axis-l.6-3-6-3   
  axis.line.y..zeroGrob.1864   
  axis   
    axis.1-1-1-1   
      GRID.text.1861   
    axis.1-2-1-2

您需要设置路径（请参阅gPath in the editGrob()下面的函数）从“axis-l”，到“axis”，到“axis”，再到“GRID.text”。标签的 x 坐标当前为 1npc。我在这里所做的就是将每隔一个标签移动到 0npc。

# The edit 
g = editGrob(grid.force(g), 
      gPath("axis-l", "axis", "axis", "GRID.text"), 
      x = unit(c(1, 0), "npc"), 
      grep = TRUE)

# Draw the plot
grid.newpage()
grid.draw(g)

第二种可能- 需要更多的工作

# Get the ggplot grob
g = ggplotGrob(plot)

# Get a hierarchical list of component grobs.
# Need a path to the labels as before,
# and a path to the tick marks.
grid.ls(grid.force(g))

# Get info about the plot: tick mark length, right margin of the tick mark labels, and
# number of labels 
 plot_theme <- function(p) {
   plyr::defaults(p$theme, theme_get())
 }

tickMarkLength <- plot_theme(plot)$axis.ticks.length 
textRightMargin <- plot_theme(plot)$strip.text.y$margin[2]
numberOfLabels <-  length(unique(ggplot_build(plot)$data[[1]]$y))

## The edits:
# Edit the x positions of every second label
g = editGrob(grid.force(g), 
      gPath("axis-l", "axis", "axis", "GRID.text"), 
      x = unit.c(unit(1, "npc"), unit(1, "npc") + 2*tickMarkLength + textRightMargin - unit(1, "pt")),
      hjust = c(1, 0), 
      grep = TRUE)

# Edit the x coordinates of the tick marks
# Need to check for even or odd number of labels
xcoord = rep(unit.c(unit(1, "npc") - tickMarkLength, unit(1, "npc"),
              unit(1, "npc") + tickMarkLength, unit(1, "npc")), numberOfLabels/2)
if((numberOfLabels %% 2) == 0)   {
      xcoord = xcoord
   } else {
      xcoord = unit.c(xcoord, unit.c(unit(1, "npc") - tickMarkLength, unit(1, "npc")))
   }
g = editGrob(grid.force(g), 
      gPath("axis-l", "axis", "axis.1-2"), 
      x = xcoord, 
      grep = TRUE)


# Draw the plot
grid.newpage()
grid.draw(g)