R语言 以图形的形式描述图表的部分内容 – legend()函数

R编程语言中的legend()函数 用于向现有的图谱添加图例。图例被定义为描述图表中每个部分的区域。图例图是用来以图形形式显示统计数据的。

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

参数

• x和y： 这些是用来定位图例的坐标。
• legend： 图例的文本
• fill： 用于填充图例文本框的颜色
• col： 线条的颜色
• bg： 它定义了图例框的背景颜色。
• title: 图例标题（可选
• text.font ：一个整数，指定图例的字体样式（可选

返回： 图例情节

R – legend() 示例

例1： R语言中legend()函数的基本例子

# 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

例2： 添加图例框的标题、文字字体和背景颜色

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

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。

例3：另一个例子是创建图例框的边界

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

参数：
box.lty、box.lwd和box.col： 分别为图例框边界的线型、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

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

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

参数：box.lty： 框线宽度

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

在例3和例4中box.lty、box.lwd和box.col可以用来修改线型、宽度和颜色，用于图例框的边框，分别用来修改参数。