R语言低级绘图函数-rect

rect 函数用来在一张图上添加矩形，只需要指定左下角和右上角的坐标的位置，就可以画出一个矩形

基本用法：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
rect(xleft = 1, ybottom = 1, xright = 5, ytop = 5)

效果图如下：

xleft, ybottom, xright, ytop 支持一次设置多个值，同时创建多个矩形，用法如下：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
rect(xleft = c(1, 2), ybottom = c(1, 2), xright = c(5, 4), ytop = c(5, 4))

效果图如下：

参数设置：

border : 设置矩形边框的颜色，默认为"black"， 支持为多个矩形设置不同的值

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
rect(xleft = c(1, 2), ybottom = c(1, 2), xright = c(5, 4), ytop = c(5, 4), border = c("red", "blue"))

效果图如下：

col : 设置矩形的填充色，默认为NULL, 表示无填充色，， 支持为多个矩形设置不同的值

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
rect(xleft = c(1, 2), ybottom = c(1, 2), xright = c(5, 4), ytop = c(5, 4), col = c("pink", "green"))

效果图如下：

density 和 angle : 搭配使用，设置用线条填充矩形，angle 设置线条的角度，默认为45， density 设置填充线条的密度，数值越大越密集

代码示例：

par(mfrow = c(1,3))
plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n", main = "density = 1")
rect(xleft = 1, ybottom = 1, xright = 5, ytop = 5, angle = 45, density = 1)
plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n", main = "density = 3")
rect(xleft = 1, ybottom = 1, xright = 5, ytop = 5, angle = 45, density = 2)
plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n", main = "density = 4")
rect(xleft = 1, ybottom = 1, xright = 5, ytop = 5, angle = 45, density = 3) 

效果图如下：

lwd:  设置矩形所有线条的宽度

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
rect(xleft = 1, ybottom = 1, xright = 5, ytop = 5, angle = 45, density = 2, lwd = 3)

效果图如下：

lty: 设置矩形所有线条的类型

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
rect(xleft = 1, ybottom = 1, xright = 5, ytop = 5, angle = 45, density = 2, lwd = 2, lty = 3)

效果图如下：