R语言低级绘图函数-points

points 用来在一张图表上添加点，指定好对应的x和y坐标，就可以添加不同形状，颜色的点了；

基本用法：

通过x和y设置点的坐标

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
points(x = c(3, 3), y = c(3, 5))

效果图如下：

参数设置：

cex : 设置点的大小

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
points(x = c(3, 3), y = c(3, 5), cex = c(2, 4))

效果图如下：

lwd : 设置点的边框的宽度

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
points(x = c(3, 3), y = c(3, 5), cex = 4, lwd = c(2, 4))

效果图如下：

pch ： 设置点的形状，取值范围为1到25，

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
index <- 1:25
start <- 0
for (i in 1:5) {
for (j in 1:5) {
start <- start + 1
points(x = i, y = j, pch = index[start], cex = 1.5)
text(x = i, y = j, labels = index[start], pos = 3, offset = 1)
}
}

效果图如下：

col:  设置点的边框的颜色

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
index <- 1:25
start <- 0
for (i in 1:5) {
	for (j in 1:5) {
		start <- start + 1
		points(x = i, y = j, pch  = index[start], cex = 1.5, col = "red")
		text(x = i, y = j, labels = index[start], pos = 3, offset = 1)
	}
}

效果图：

bg ： 设置点的背景色，其实就是填充色，需要注意的是，只有形状为21到25的点是有填充色的

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n")
index <- 1:25
start <- 0
for (i in 1:5) {
	for (j in 1:5) {
		start <- start + 1
		points(x = i, y = j, pch  = index[start], cex = 1.5, bg = "red")
		text(x = i, y = j, labels = index[start], pos = 3, offset = 1)
	}
}

效果图如下：