R語言 legend()用法及代碼示例

R 語言中的 legend() 函數用於向現有 Plot 添加圖例。圖例被定義為描述圖的每個部分的圖的一個區域。圖例圖用於以圖形形式顯示統計數據。

用法：
legend(x, y, legend, fill, col, bg, lty, cex, title, text.font, bg)

參數：
x and y:這些是用於定位圖例的坐標
legend:傳說中的文字
fill:用於填充圖例文本框的顏色
col:線條的顏色
bg:它定義圖例框的背景顏色。
title:圖例標題(可選)
文本字體：指定圖例字體樣式的整數(可選)

返回：圖例圖

範例1：


# Generate some data
x <- 1:8; 
y1 = x; y2 = 2 * y1
plot(x, y1, type = "b", pch = 22, 
     col = "green", 
     xlab = "X", ylab = "Y")
   
# Add a line
lines(x, y2, pch = 18, col = "darkgreen",
           type = "b", lty = 2)
   
# Add a legend
legend(1, 50, legend = c("Legend Line 1", "Legend Line 2"),
       col = c("green", "darkgreen"), lty = 2:3, cex = 0.6)

輸出：

範例2：添加圖例框的標題、文字字體和背景色


makePlot<-function(){
  x<-1:10; 
  y1 = x * x; y2 = 2 * y1
  plot(x, y1, type = "b", pch = 19, 
                     col = "green", 
            xlab = "X", ylab = "Y")
  lines(x, y2, pch = 22, col = "darkgreen", 
             type = "b", lty = 6)
}
makePlot()
   
# Add a legend to the plot
legend(1, 95, legend = c(" Legend Line 1", "Legend Line 2"),
       col = c("green", "darkgreen"), lty = 1:2, cex = 0.9,
       title = "Line types", text.font = 6, bg = 'gray')

輸出：

在這裏，legend()函數用於向繪圖添加圖例，makePlot() 函數用於操作字體、背景顏色。

範例3：創建圖例框邊框的另一個示例

用法：
legendx, y, fill, col, bg, lty, cex=0.8, box.lty, box.lwd, box.col)

參數：
box.lty、box.lwd 和 box.col：分別用於圖例框邊框的線型、寬度和顏色。


makePlot<-function(){
  x<-1:10; 
  y1 = x * x; y2 = 2 * y1
  plot(x, y1, type = "b", pch = 22, 
                     col = "green", 
             xlab = "x", ylab = "y")
    
  lines(x, y2, pch = 18, col = "darkgreen", 
             type = "b", lty = 4)
}
   
# Change the border
makePlot()
legend(1, 100, legend = c("Legend Line 1", "Legend Line 2"),
       col = c("green", "darkgreen"), lty = 1:2, cex = 0.8,
       box.lty = 4, box.lwd = 2, box.col = "green")

輸出：

範例4：下麵是在 legend() 函數中使用 box.lty = 0 去除圖例邊框的說明

用法：
legendx, y, fill, col, bg, lty, cex=0.8, box.lty=0)

參數：
box.lty：框線寬


makePlot<-function(){
  x<-1:10; 
  y1 = x * x; y2 = 2 * y1
  plot(x, y1, type = "b", pch = 22, 
                     col = "green", 
            xlab = "x", ylab = "y")
    
  lines(x, y2, pch = 18, col = "darkgreen", 
             type = "b", lty = 4)
}
   
# Remove legend border using box.lty = 0
makePlot()
legend(2, 100, legend = c("Legend Line 1", 
                          "Legend Line 2"),
       col = c("green", "darkgreen"), 
       lty = 1:2, cex = 0.8, box.lty = 0)

輸出：

例3和例4中box.lty、box.lwd和box.col可用於修改圖例框邊框的線型、寬度和顏色，分別用於修改參數。

相關用法

注：本文由純淨天空篩選整理自kaurbal1698大神的英文原創作品 Describe Parts of a Chart in Graphical Form in R Programming – legend() Function。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。