多元图中颜色的r层

Question

如何使不同的颜色层更好地看到R中的多元函数？我想检查函数是否是拟凹和拟凸，但这些东西很难在一个单色图中看到.

# Define Sequences for Multivariate Function
xf3x1 <- seq(-100, 100, length=500)
xf3x2 <- seq(-100, 100, length=500)

# Outer Calculates the Cartesian Product
z <- outer(xf3x1,xf3x2,function(xf3x1,xf3x2) xf3x1*xf3x2)
persp(xf3x1,xf3x2,z,col="lightgreen",theta=30,phi=20, main="Problème 3: Function 3")

Answer 1

plot3D包是一个额外的选项。默认情况下，z值为persp3D颜色：

library(plot3D)  # For persp3D function

# Define Sequences for Multivariate Function
#### length=50 to speed up plotting ####
xf3x1 <- seq(-100, 100, length=50)
xf3x2 <- seq(-100, 100, length=50)

# Outer Calculates the Cartesian Product
z <- outer(xf3x1,xf3x2,function(xf3x1,xf3x2) xf3x1*xf3x2)

persp(xf3x1,xf3x2, z, theta=30, phi=20, 
      col="lightgreen",
      main="persp: Black border lines overwhelm plot")

persp(xf3x1,xf3x2, z, theta=30, phi=20, 
      col="lightgreen",
      border="black", lwd=0.2,  # Or border=NA per @jlhoward
      main="persp: Thinner border lines")

persp3D(xf3x1,xf3x2, z, theta=30, phi=20, 
        main="persp3D: No borders by default")

persp3D(xf3x1,xf3x2, z, theta=30, phi=20, 
        border="black", lwd=0.5,
        main="persp3D with borders")

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Answer 2

首先，需要设置border=NA以关闭表面面周围的边框。

一种方法是基于z值的颜色.适应this post

nrz <- nrow(z)
ncz <- ncol(z)
color <- rev(rainbow(100))
zfacet <- z[-1, -1] + z[-1, -ncz] + z[-nrz, -1] + z[-nrz, -ncz]
facetcol <- cut(zfacet, 100)
persp(xf3x1,xf3x2,z,col=color[facetcol],border=NA,,theta=30,phi=20)

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我鼓励您尝试在surface3d(...)包中使用rgl，它可以创建可旋转的3D图形。下面的图片只是一个屏幕截图。

zlen <- diff(range(z)) + 1
clrs <- rev(rainbow(zlen))
col <- clrs[ z - min(z) + 1 ] # assign colors to heights for each point
open3d(scale=c(100,100,1))
surface3d(xf3x1,xf3x2,z,col=col, main="Problème 3: Function 3")
axes3d(box=TRUE)
title3d(xlab="xf3f1", ylab="xf3x2", zlab="z")

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