在表面上找到轮廓的精确坐标并在 R 中手动绘制

Question

我正在绘制曲面图并想使用 plotly“手动”绘制等高线。在下面的代码中我：

• 模拟绘制曲面图的数据
• 使用contoureR包
计算特定z水平的等高线坐标
• 绘制曲面图和等高线

# Load packages
library(plotly) # for interactive visualizations
library(contoureR) # for calculating contour coordinates

# Simulate the data for plotting
x <- y <- seq(from = 0, to = 100, by = 1)
z1 <- outer(X = x, Y = y, FUN = function(x, y) x^0.2 * y^0.3) # data for surface plot

# Obtain coordinates of contour for z = 5
z_level <- 5
r <- contourLines(x = x, y = y, z = z1, levels = z_level)

plot_ly(
  type = "surface",
  x = x,
  y = y,
  z = z1,
) %>%
  add_trace(
    type = "scatter3d",
    x = r[[1]]$x,
    y = r[[1]]$y,
    z = z_level
  )

我知道这些都是近似值，所以我也尝试将contourLines()产生的x和y坐标传递给用于创建[=17=的公式]上面并使用相应的值绘制我的等高线（而不是使用z_level = 5，但我仍然没有得到想要的结果：

plot_ly(
  x = x,
  y = y,
  z = z1,
  type = "surface"
) %>%
  add_trace(
    type = "scatter3d",
    x = r[[1]]$x,
    y = r[[1]]$y,
    z = r[[1]]$x^0.2*r[[1]]$y^0.3
  )

我也知道 plotly 使我能够绘制特定的轮廓线（请在此处查看我的问题和答案：）。但是，我想自己绘制轮廓线（在获得坐标后），以便它可以通过光标“拉动”并在我将鼠标悬停在它上面时向我显示工具提示信息。理想情况下，如果有一种方法可以获得 plotly 本身计算的等高线坐标，那就太好了。

感谢您的帮助。

Answer 1

我找到了解决这个问题的两个方法。

解决方案 1：转置 z1 矩阵

第一个解决方案是@nirgrahamuk 给我的，它包括转置 z1 矩阵：

library(plotly) # for interactive visualizations

# Simulate the data for plotting
x <- y <- seq(from = 0, to = 100, by = 1)
z1 <- outer(X = x, Y = y, FUN = function(x, y) x^0.2 * y^0.3) # data for surface plot

# Obtain coordinates of contour for z = 5
z_level <- 6
r <- contourLines(x = x, 
                  y = y, 
                  z = z1, 
                  levels = z_level)

plot_ly(
  type = "surface",
  z = t(z1), # *** WE TRANSPOSE THE MATRIX HERE! ***
) %>%
  add_trace(
    type = "scatter3d",
    x = r[[1]]$x,
    y = r[[1]]$y,
    z = z_level
  )

解决方案 2：使用 isoband 包

第二种解决方案是使用isoband::isolines()函数计算等高线坐标：

library(plotly) # for interactive visualizations
library(isoband) # for find contour lines coordinates

# Simulate the data for plotting
x <- y <- seq(from = 0, to = 100, by = 1)
z1 <- outer(X = x, Y = y, FUN = function(x, y) x^0.2 * y^0.3) # data for surface plot

# Obtain coordinates of contour for z = 5
z_level <- 6
r <- isolines(x = x, # *** WE USE THE isolines() FUNCTION HERE ***
              y = y, 
              z = z1, 
              levels = z_level)

plot_ly(
  type = "surface",
  z = z1, 
) %>%
  add_trace(
    type = "scatter3d",
    x = r[[1]]$x,
    y = r[[1]]$y,
    z = z_level
  )