如何使用较少的包绘制二元正态分布的曲面和轮廓 [英] How to plot the surface and contours of a bivariate normal distribution using fewer packages

问题描述

我将绘制二元正态分布的 3D 表面及其轮廓(它可以是任何二元正态分布).我想在我的绘图中使用 persp 和 contour.我在互联网上搜索，但我找到了很多方法.他们中的大多数都使用了一些软件包.但是我想以使用更少的包甚至不安装任何包的方式来做到这一点(但是，我不知道这是可能的).你能用一个二元正态分布的例子告诉我你自己的方式吗?[更少的包，更好的解决方案].实际上，我希望看到绘制二元正态分布的曲面和轮廓的最简单方法.

I am going to plot the 3D surface of a bivariate normal distribution and its contours (it could be any bivariate normal distribution). I want to use persp and contour in my drawing. I searched on the Internet, but I found many ways to do it. Most of them have used some packages. But I would like to do this in a way that uses fewer packages or even without installing any package (however, I do not know it is possible). Could you please show me your own way with an example of a bivariate normal distribution? [Fewer packages, better solution]. Indeed I would like to see the simplest way of drawing a surface and contours of a bivariate normal distribution.

推荐答案

你可以在不使用包的情况下在 R 中做任何你喜欢做的事情，只要你准备好编写自己的代码来做这件事.使用 persp 和 contour 仅用几行 R 代码就可以可视化二维表面，但是生成表面(即创建二维密度情节，不是微不足道的.

You can do just about anything you like in R without using packages, as long as you are prepared to write your own code to do it. Visualising a 2d surface is possible in just a few lines of R code using persp and contour, but generating the surface (i.e. creating a 2d density plot, is not trivial.

以下是仅使用 mnormt 包(如评论中所要求)生成二维二元正态分布表面的方法.对于这个例子，我创建了一个虚拟方差-协方差矩阵.

Here is how you can generate a 2d bivariate normal distribution surface using just the mnormt package (as requested in the comments). For this example, I have made up a dummy variance-covariance matrix.

library(mnormt)

x     <- seq(-5, 5, 0.25) 
y     <- seq(-5, 5, 0.25)
mu    <- c(0, 0)
sigma <- matrix(c(2, -1, -1, 2), nrow = 2)
f     <- function(x, y) dmnorm(cbind(x, y), mu, sigma)
z     <- outer(x, y, f)

contour(x, y, z)

persp(x, y, z, theta = -30, phi = 25, 
      shade = 0.75, col = "gold", expand = 0.5, r = 2, 
      ltheta = 25, ticktype = "detailed")

^{由 reprex 包 (v0.3.0) 于 2020 年 6 月 17 日创建}

^{Created on 2020-06-17 by the reprex package (v0.3.0)}

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