R语言 legend()用法及代码示例

R 语言中的 legend() 函数用于向现有 Plot 添加图例。图例被定义为描述图的每个部分的图的一个区域。图例图用于以图形形式显示统计数据。

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

参数：
x and y:这些是用于定位图例的坐标
legend:传说中的文字
fill:用于填充图例文本框的颜色
col:线条的颜色
bg:它定义图例框的背景颜色。
title:图例标题(可选)
文本字体：指定图例字体样式的整数(可选)

返回：图例图

范例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)

输出：

范例2：添加图例框的标题、文字字体和背景色


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')

输出：

在这里，legend()函数用于向绘图添加图例，makePlot() 函数用于操作字体、背景颜色。

范例3：创建图例框边框的另一个示例

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

参数：
box.lty、box.lwd 和 box.col：分别用于图例框边框的线型、宽度和颜色。


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")

输出：

范例4：下面是在 legend() 函数中使用 box.lty = 0 去除图例边框的说明

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

参数：
box.lty：框线宽


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)

输出：

例3和例4中box.lty、box.lwd和box.col可用于修改图例框边框的线型、宽度和颜色，分别用于修改参数。

相关用法

注：本文由纯净天空筛选整理自kaurbal1698大神的英文原创作品 Describe Parts of a Chart in Graphical Form in R Programming – legend() Function。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。