R语言低级绘图函数-title

title 函数用来在一张图表上添加标题

基本用法：

main 表示主标题，通常位于图像的上方， sub 表示副标题，位于图像的下方， xlab 表示x轴的标签，ylab 表示y轴的标签

par(oma = c(1, 1, 1, 1))
plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n", xlab = "", ylab = "")
box(which = "figure", col = "red", lwd = 2)
box(which = "plot", col = "blue", lwd = 2)
title(main = "main tilte", sub = "sub title", xlab = "xlab", ylab = "ylab")

效果图如下：

参数设置：

col : 设置标题的颜色

cex : 设置标题的文字大小

font : 设置标题的文字的格式

以上三个参数可以针对不同的标题分别进行设置，需要注意的是xlab和ylab 不能分开设置，只能是同时设置，对应的参数为 col.lab, col.cex, font.cex

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n", xlab = "", ylab = "")
title(main = "main tilte", sub = "sub title", xlab = "xlab", ylab = "ylab", col.main = "red", cex.sub = 1.5, col.lab = "blue")

效果图：

outer : 逻辑值，如果为TRUE, 将标题放到plot area的外边

代码示例：

par(oma = c(5, 5, 3, 3))
plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n", xlab = "", ylab = "")
box(which = "figure", col = "red", lwd = 2)
box(which = "plot", col = "blue", lwd = 2)
title(main = "main tilte", sub = "sub title", xlab = "xlab", ylab = "ylab", outer=TRUE)

效果图如下：

 title 中也允许表达式

代码示例：

plot(1:5, 1:5, xlim = c(0,6), ylim = c (0,6), type = "n", xlab = "", ylab = "")
title(main = expression(sqrt(x)), sub = expression(x^2), xlab = "xlab", ylab = "ylab")

 效果图如下：

更多关于表达式的书写，可以参考plotmath 函数的帮助文档