1.matlab：

fill1.m

fill2.m

fill3.m

2.R：

https://www.stat.auckland.ac.nz/~paul/RGraphics/examples-simonmatt.R

> # Distance Between Brownian Motions 布朗运动之间的距离

> n <- 100

> xx <- c(0:n, n:0)   #生成202个元素的向量，其中前面101与后面101数字对称

> yy <- c(c(0, cumsum(stats::rnorm(n))), rev(c(0, cumsum(stats::rnorm(n)))))

> plot   (xx, yy, type = "n", xlab = "Time", ylab = "Distance")

> polygon(xx, yy, col = "gray", border = "red")

http://wap.sciencenet.cn/blog-651374-1126673.html

参考教程：ggplot2 Guide to Create Beautiful Graphics in R

3.PS