在 R 编程中以图形形式描述图表的各个部分 – legend()函数

R 编程语言中的legend()函数用于将图例添加到现有绘图中。图例被定义为描述图表每个部分的图表区域。图例图用于以图形形式显示统计数据。

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

Parameters: 

• x and y: These are co-ordinates to be used to position the legend
• legend: Text of the legend
• fill: Colors to use for filling the boxes of legend text
• col: Colors of lines
• bg: It defines background color for the legend box.
• title: Legend title (optional)
• text.font: An integer specifying the font style of the legend (optional)
• Returns: Legend plot

R – 图例() 示例

示例 1： R 中 legend()函数的基本示例

R

# 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：

示例 2：添加图例框的标题、文本字体和背景颜色

R

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()函数用于为绘图添加图例，makePlot()函数用于操作字体、背景颜色。

示例 3：创建图例框边框的另一个示例

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

Parameters: 
box.lty, box.lwd and box.col: line type, width and color for the legend box border, respectively. 

R

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：

示例 4：下图是通过在 legend()函数中使用 box.lty = 0 来移除图例边框的图示

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

Parameter: box.lty: Box line width 

R

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：

在示例 3 和示例 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。