R语言 指定点之间绘制多边形 – polygon()函数

R语言中的 polygon() 函数用于在现有绘图中的指定点之间绘制一个多边形。

语法： polygon(x_coordinates, y_coordinates)

参数：

x_coordinates, y_coordinates： 要绘制多边形的绘图的x、y坐标。

返回： 给定情节中的多边形

例子1： 在R图中画一个正方形多边形

# R program to draw a polygon
  
# Draw an empty plot
plot(2, 2, col = "white", xlab = "X", ylab = "Y")  
  
# Draw a polygon
polygon(x = c(2.7, 2.3, 2.2, 2.8),  # X-Coordinates of polygon 
        y = c(2.6, 2.8, 2.4, 2),    # Y-Coordinates of polygon
        col = "darkgreen") 

输出：

例2： 给多边形的边框上色

# R program to draw a polygon
  
# Draw empty plot
plot(2, 2, col = "white", xlab = "X", ylab = "Y") 
  
# Draw a polygon
polygon(x = c(2.7, 2.3, 2.2, 2.8),  # X-Coordinates of polygon
        y = c(2.6, 2.8, 2.4, 2),    # Y-Coordinates of polygon
        col = "darkgreen",          # Color of polygon
        border = "red",             # Color of polygon border
        lwd = 8)                    # Thickness of border

输出：

这里，border指定了边界颜色，lwd指定了边界厚度。

例3： 绘制频率多边形

# R program to draw a polygon
  
# X values for frequency polygon
x1 <- 1:10                          
  
# Y values for frequency polygon
y1 <- c(2, 4, 7, 4, 5, 8, 6, 6, 1, 2)  
  
# Plot frequency polygon
plot(x1, y1,                                       
     type = "l",     # Set line type to line
     lwd = 4)         # Thickness of line
       
# X-Y-Coordinates of polygon
polygon(c(1, x1, 10), c(0, y1, 0),          
        col = "darkgreen")   # Color of polygon
  
# Add squares to frequency polygon
points(x1, y1,                          
       cex = 1,    # Size of squares                             
       pch = 12)  
       segments(x1, 0, x1, y1)  

输出：

例4： 在密度下面画多边形

# R program to draw a polygon
  
# Set seed for reproducibility
set.seed(15000)      
  
# Sample size
N <- 1000             
  
# Draw random poisson distribution
x1 <- rpois(N, 2)                           
plot(density(x1),    # Draw density plot
     main = "",      # No main title
     xlab = "x1")    # Set name of x-axis to x2
       
# X-Coordinates of polygon
polygon(c(min(density(x1)x), density(x1)x),           
        c(0, density(x1)$y),     # Y-Coordinates of polygon
        col = "darkgreen")       # Color of polygon

输出：

这里，上面的例子是用来做概率密度函数的。