将永久等高线添加到 R plotly 中的曲面图

Question

我正在使用 R 中的plotly 包来绘制曲面图和等高线图：

# Load package
library(plotly)

# 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

# Draw surface plot (3D)
plotly::plot_ly(z = z1) %>%
  plotly::add_surface(
    contours = list(
      z = list(
        show = TRUE,
        usecolormap = TRUE,
        highlightcolor = "#ff0000",
        project = list(z = TRUE)
      ) 
    )    
  ) 

# Draw contour plot (2D)
plot_ly(z = z1) %>%
  add_contour()

这两个图的渲染包含等高线，显示了x 和y 的组合，它们产生了一个常数z 水平。在 3D 曲面图的情况下，将鼠标悬停在其上会动态绘制一条等高线，鼠标所在的位置会在 3 维空间的一侧上投影等高线。

我想做的是通过自己指定z 的值（例如z = 5）在两个图上手动绘制一条或多条等高线。

Answer 1

感谢@IRTFM 的评论，我能够找到我的问题的答案。答案更具体到等高线图。用户需要将contours 参数下的start 和end 属性设置为所需的z 值。下面，我绘制了z = 5 的等高线：

# Load package
library(plotly)

# 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

plot_ly(
  z = z1,
  type = "contour",
  autocontour = FALSE,    
  colorscale = "RdBu",
  
  contours = list(
    start = 5,
    end = 5,
    showlabels = TRUE,
    showlines = TRUE,
    coloring = "lines"
  )
  
) %>%
 hide_guides()

如果想要绘制 2 条特定的等高线，他们需要一个额外的参数：ncontours = 2。不这样做可能会导致绘制超过 2 条等高线 - z 值介于 start 和 end 之间的线。

plot_ly(
  z = z1,
  type = "contour",
  autocontour = FALSE,
  
  ncontours = 2,
  
  colorscale = "RdBu",
  
  contours = list(
    start = 5,
    end = 7,
    showlabels = TRUE,
    showlines = TRUE,
    coloring = "lines"
  )
  
) %>%
 hide_guides()

最后，对于2个以上的特定等高线，我们需要使用add_contour()函数。让我们绘制 4 个特定的等高线图：

plot_ly(
  z = z1,
  type = "contour",
  autocontour = FALSE,
  
  ncontours = 2,
  
  colorscale = "RdBu",
  
  contours = list(
    start = 5,
    end = 7,
    showlabels = TRUE,
    showlines = TRUE,
    coloring = "lines"
  )
  
) %>% 
  
  add_contour(
    
    ncontours = 2,
    
    contours = list(
      start = 4,
      end = 6,
      showlabels = TRUE,
      showlines = TRUE,
      coloring = "lines"
    )
    
  ) %>%
  
  hide_guides()