ggplot2：對於沒有標籤的刻度線有更短的刻度標記

Question

我有一個使用ggplot2的繪圖，其中我想沿x軸繪製很多刻度線，但只有一些刻度線會有與它們相關的刻度標籤。不過，我希望那些有標籤的標記比那些標記更長。

Answer 1

theme(axis.ticks.length)

http://docs.ggplot2.org/0.9.2.1/theme.html應該是有用的。

編輯對不起，只是仔細閱讀你的問題。標籤的是標準的major.grid ticks嗎？或以某種自定義的方式標記？

Answer 2

在基R，可以與初始plot呼叫（具有xaxt='n'）抑制x軸，然後使用tcl控制蜱長度（參見?par）具有兩個axis(1, ...)呼叫。

plot(1:10, xaxt='n', ylab='', las=1) 
axis(1, at=1:10, tcl=-0.8) 
axis(1, at=seq(0, 11, 0.2), labels=NA) 

Answer 3

這是基礎的圖形更容易，但這裏是使用GGPLOT2的嘗試。

該方法基於this method，它將空白標籤插入標籤序列（使用該答案中的代碼）。一旦中斷和標籤在ggplot中就位，我會鑽入圖的結構來編輯刻度線的長度。 （請謹慎使用，它不會是很難打破這一點。）

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)