I’m having trouble targeting a specific plotly trace with my R shiny inputs. Is it even possible to restyle a trace by its name? Alternatively can I delete and add the trace by name? I’ve seen examples of deleting the trace without using the name, but that seems to only work where you have one trace. Below is the full shiny app.

library(shiny)
library(plotly)

plot_cylinder <- function(x, y, z, radius, height, color = 'red') {
  theta <- seq(0, 2*pi, length.out = 30)
  z_cyl <- seq(z, z + height, length.out = 2)
  x_cyl <- outer(x + radius * cos(theta), rep(1, length(z_cyl)))
  y_cyl <- outer(y + radius * sin(theta), rep(1, length(z_cyl)))
  z_cyl <- outer(rep(1, length(theta)), z_cyl)
  
  list(
    type = "surface",
    x = x_cyl,
    y = y_cyl,
    z = z_cyl,
    colorscale = list(c(0, color), c(1, color))
  )
}

plot_sphere <- function(x, y, z, r, color = 'blue') {
  theta <- seq(0, 2*pi, length.out = 30)
  phi <- seq(0, pi, length.out = 30)
  x_sphere <- x + r * outer(cos(theta), sin(phi))
  y_sphere <- y + r * outer(sin(theta), sin(phi))
  z_sphere <- z + r * outer(rep(1, length(theta)), cos(phi))
  
  list(x = x_sphere, y = y_sphere, z = z_sphere, color = color)
}

# Static sphere data
sphere_radius <- 7.24
sphere_data <- plot_sphere(0, 0, 10, sphere_radius)

cylinder_data <- plot_cylinder(0, 0, 0, 3, 10)

ui <- fluidPage(
  titlePanel("Cylinder Plotting"),
  sidebarLayout(
    sidebarPanel(
      sliderInput("radius", "Cylinder Radius:", min = 1, max = 10, value = 3),
      sliderInput("height", "Cylinder Height:", min = 1, max = 20, value = 10),
      actionButton("initialize", "Initialize Cylinder")
    ),
    mainPanel(
      plotlyOutput("plot")
    )
  )
)

server <- function(input, output, session) {
  output$plot <- renderPlotly({
    plot_ly() |> 
      add_surface(x = sphere_data$x, y = sphere_data$y, 
                  z = sphere_data$z, colors = sphere_data$color, 
                  opacity = 0.5, name = "sphere") |> 
      add_surface(x = cylinder_data$x, y = cylinder_data$y, 
                  z = cylinder_data$z, colorscale = cylinder_data$colorscale, 
                  opacity = 0, name = "cylinder")
  })
  
  observeEvent(input$initialize, {
    proxy <- plotlyProxy("plot", session)
    
    plotlyProxyInvoke(proxy, "restyle", list(opacity = list(0.1)), list(name = "cylinder"))
  })
  
  
  observeEvent(c(input$radius, input$height), {
    proxy <- plotlyProxy("plot", session)
    
    # Get the updated cylinder trace
    cylinder_data <- plot_cylinder(0, 0, 0, input$radius, input$height)
    
    # Update the trace with the new x, y, z values
    plotlyProxyInvoke(proxy, "restyle", list(
      x = list(cylinder_data$x),
      y = list(cylinder_data$y),
      z = list(cylinder_data$z)
    ), list(name = "cylinder"))
  })
}

shinyApp(ui = ui, server = server)