ggplot2：不带标签的刻度线较短的刻度线（对于y轴） [英] ggplot2: shorter tick marks for tick marks without labels (for y axis)

问题描述

我试图在这里复制@ sandy-muspratt的答案：

I'm trying to replicate an answer by @sandy-muspratt here : ggplot2: Have shorter tick marks for tick marks without labels

but I'd like to add shorter tick marks for the y axis. The original code is

library(ggplot2)
library(grid)

# Data
 df = data.frame(x = 1:10, y = 1:10)

# Range of x values
range = 1:10

# Major tick marks
major = 1

# Minor tick marks
minor = 0.2

# Function to insert blank labels
# Borrowed from https://stackoverflow.com/questions/14490071/adding-minor-tick-marks-to-the-x-axis-in-ggplot2-with-no-labels/14490652#14490652
insert_minor <- function(major, n_minor) {
      labs <- c(sapply(major, function(x, y) c(x, rep("", y) ), y = round(n_minor)))
      labs[1:(length(labs) - n_minor)]
}

# Getting the 'breaks' and 'labels' for the ggplot
n_minor = major/minor - 1
breaks = seq(min(range), max(range), minor)
labels = insert_minor(seq(min(range), max(range), major), n_minor)
if(length(breaks) > length(labels)) labels = c(labels, rep("", length(breaks) - length(labels)))

# The plot
p <- ggplot(df, aes(x = x, y = y)) + 
     geom_point() + 
     scale_x_continuous(breaks = breaks, labels = labels) + 
     coord_cartesian(xlim = range) +
     theme_bw() +
     theme(panel.grid = element_blank(),
           axis.text.x = element_text(margin = margin(t = 5, unit = "pt")))
p

# Edit the plot:
# Change the lengths of the major tick marks

g = ggplotGrob(p)

# Get the x axis
xaxis <- g$grobs[[which(g$layout$name == "axis-b")]]  

# Get the tick marks and tick mark labels   
ticks <- xaxis$children[[2]]

# Get the tick marks
marks = ticks$grobs[[1]]

# Edit the y positions of the end points of the tick marks
# The '6' and the '3' in the code below 
# are the lengths in pts of the major and minor tick marks respectively. 
marks$y = unit.c(unit.c(unit(1, "npc") - unit(6, "pt"), unit(1, "npc"),   
                 rep(unit.c(unit(1, "npc") - unit(3, "pt"), unit(1, "npc")), n_minor)))

# Put the tick marks back into the plot
ticks$grobs[[1]] = marks
xaxis$children[[2]] = ticks
g$grobs[[which(g$layout$name == "axis-b")]]  = xaxis

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

I tried to modify the code to make it work for the y axis, but was not able to get longer lines for the major tick marks:

library(ggplot2)
library(grid)

# Data
 df = data.frame(x = 1:10, y = 1:10)

# Range of y values
range = 1:10

# Major tick marks
major = 1

# Minor tick marks
minor = 0.2

# Function to insert blank labels
# Borrowed from https://stackoverflow.com/questions/14490071/adding-minor-tick-marks-to-the-x-axis-in-ggplot2-with-no-labels/14490652#14490652
insert_minor <- function(major, n_minor) {
      labs <- c(sapply(major, function(x, y) c(x, rep("", y) ), y = round(n_minor)))
      labs[1:(length(labs) - n_minor)]
}

# Getting the 'breaks' and 'labels' for the ggplot
n_minor = major/minor - 1
breaks = seq(min(range), max(range), minor)
labels = insert_minor(seq(min(range), max(range), major), n_minor)
if(length(breaks) > length(labels)) labels = c(labels, rep("", length(breaks) - length(labels)))

# The plot
p <- ggplot(df, aes(x = x, y = y)) + 
     geom_point() + 
     scale_y_continuous(breaks = breaks, labels = labels) + 
     coord_cartesian(ylim = range) +
     theme_bw() +
     theme(panel.grid = element_blank(),
           axis.text.y = element_text(margin = margin(t = 5, unit = "pt")))
p

# Edit the plot:
# Change the lengths of the major tick marks

g = ggplotGrob(p)

# Get the x axis
yaxis <- g$grobs[[which(g$layout$name == "axis-l")]]  

# Get the tick marks and tick mark labels   
ticks <- yaxis$children[[2]]

# Get the tick marks
marks = ticks$grobs[[1]]

# Edit the y positions of the end points of the tick marks
# The '6' and the '3' in the code below 
# are the lengths in pts of the major and minor tick marks respectively. 
marks$x = unit.c(unit.c(unit(1, "npc") - unit(6, "pt"), unit(1, "npc"),   
                 rep(unit.c(unit(1, "npc") - unit(3, "pt"), unit(1, "npc")), n_minor)))

# Put the tick marks back into the plot
ticks$grobs[[1]] = marks
yaxis$children[[2]] = ticks
g$grobs[[which(g$layout$name == "axis-l")]]  = yaxis

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

I'd greatly appreciate any help making this work. Thank you.

解决方案

The main issue is that you should be using marks = ticks$grobs[[2]]. There were some other issues with your code (which give's a warning 'data length is not a multiple of split variable') so here is a working minimal example:

labs = seq(0,100,10)
labs[!!((seq_along(labs)-1)%%5)] = ''
g = ggplot(data.frame(x = 1:10, y = (1:10)^2), aes(x,y)) +
  geom_point() +
  scale_y_continuous(breaks = seq(0,100,10), labels = labs) +
  theme(axis.ticks.length=unit(10, "pt"))

gg = ggplotGrob(g)
yaxis <- gg$grobs[[which(gg$layout$name == "axis-l")]]  
ticks <- yaxis$children[[2]]
marks = ticks$grobs[[2]]
marks$x[c(2:5,7:10)*2-1] = unit(1, "npc") - unit(3, "pt")

# Put the tick marks back into the plot
ticks$grobs[[2]] = marks
yaxis$children[[2]] = ticks
gg$grobs[[which(gg$layout$name == "axis-l")]]  = yaxis
grid.draw(gg)

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