如何在R的persp3D协方差矩阵透视图中设置底部水平图例？

我正在用R构建协方差矩阵的3D透视图，现有可复现代码如下，希望将图例放置在底部并设置为水平样式，请问如何通过persp3D()函数实现？

nrows <- 10
ncols <- 10
p <- nrows * ncols

Qvariance <- 1
Qrho <- 0.8

alpha <- matrix(rep(1:p, p), nrow = p, ncol = p)
JJ <- (alpha - 1) %% nrows + 1
II <- floor((alpha - JJ) / ncols) + 1
LL <- t(JJ)
KK <- t(II)
d <- sqrt((LL - JJ)^2 + (KK - II)^2)
Q <- Qvariance * (Qrho^d)

print(dim(Q))
Q[1:5, 1:5]

x <- 1:ncol(Q)
y <- 1:nrow(Q)

# Create a grid of x and y values
X <- matrix(x, nrow = nrow(Q), ncol = ncol(Q), byrow = TRUE)
Y <- matrix(y, nrow = nrow(Q), ncol = ncol(Q), byrow = FALSE)

library(plot3D)
persp3D(x = X, y = Y, z = Q, theta = 90, expand = 0.5, xlab = "Columns", ylab = "Rows", scale = FALSE)

解决方案 #

通过persp3D()的colkey参数可以自定义图例的样式和位置，核心配置如下：

• side = 1：指定图例放置在绘图区域底部（side参数取值：1=底部，2=左侧，3=顶部，4=右侧）
• horizontal = TRUE：将图例设置为水平排列样式
• length（可选）：调整图例的长度比例，让显示更协调

修改后的完整代码：

nrows <- 10
ncols <- 10
p <- nrows * ncols

Qvariance <- 1
Qrho <- 0.8

alpha <- matrix(rep(1:p, p), nrow = p, ncol = p)
JJ <- (alpha - 1) %% nrows + 1
II <- floor((alpha - JJ) / ncols) + 1
LL <- t(JJ)
KK <- t(II)
d <- sqrt((LL - JJ)^2 + (KK - II)^2)
Q <- Qvariance * (Qrho^d)

print(dim(Q))
Q[1:5, 1:5]

x <- 1:ncol(Q)
y <- 1:nrow(Q)

# Create a grid of x and y values
X <- matrix(x, nrow = nrow(Q), ncol = ncol(Q), byrow = TRUE)
Y <- matrix(y, nrow = nrow(Q), ncol = ncol(Q), byrow = FALSE)

library(plot3D)
# 配置colkey实现底部水平图例
persp3D(x = X, y = Y, z = Q, theta = 90, expand = 0.5, 
        xlab = "Columns", ylab = "Rows", scale = FALSE,
        colkey = list(side = 1, horizontal = TRUE, length = 0.8))

内容的提问来源于stack exchange，提问作者Ash