title: r plotly 3d surface plot issue
body: <p>I am trying to plot a 3d surface plot based on these <a href="https://plot.ly/r/3d-surface-plots/" rel="nofollow noreferrer">plotly examples</a></p>
  
  <p>When I try these examples on my dataset </p>
  
  <pre><code> test_plotly =   structure(list(Age = c(82L, 82L, 83L, 83L, 83L, 81L,  
         81L, 
      81L, 79L, 80L, 82L, 78L, 78L, 79L, 78L, 80L, 79L, 77L, 77L, 77L, 
      77L, 78L, 76L, 77L, 77L, 78L, 77L, 76L, 83L, 79L, 76L, 84L, 75L, 
      75L, 77L, 74L, 74L, 75L, 74L, 74L, 73L, 73L, 74L, 81L, 84L, 73L, 
      72L, 73L, 71L, 71L, 73L, 72L, 79L, 72L, 71L, 76L, 72L, 75L, 73L, 
      71L, 70L, 79L, 69L, 70L, 70L, 70L, 77L, 69L, 69L, 68L, 69L, 73L, 
      69L, 69L, 74L, 68L, 69L, 70L, 74L, 68L, 68L, 68L, 68L, 68L, 68L, 
      80L, 69L, 72L, 80L, 80L, 81L, 81L, 67L, 66L, 67L, 78L, 77L, 67L, 
      67L, 81L), BMI = c(32.88, 30.79, 30.08, 30.08, 30.08, 30.08, 
      30.08, 30.08, 36.86, 36.86, 32.33, 43.17, 43.17, 26.89, 25.15, 
      24.59, 33.98, 27.83, 34.66, 33.81, 29.47, 23.54, 23.54, 30.29, 
      43.21, 33.03, 20.62, 41.41, 37.88, 25.58, 26.08, 31.18, 27.78, 
      23.35, 25.42, 27.75, 27.75, 28.83, 27.68, 27.14, 29.13, 27.23, 
      27.75, 25.25, 28.79, 34.46, 30.93, 22.57, 19.06, 27.81, 33.35, 
      28.63, 36.11, 37.94, 31.89, 31.23, 38.65, 23.39, 31.13, 31.13, 
      24.07, 27.01, 32.78, 37.82, 31.98, 28.77, 27.52, 32.88, 26.17, 
      46.24, 32.09, 32.78, 25.4, 32.72, 31.21, 29.13, 45.85, 27.99, 
      36.33, 32.21, 35.97, 28.88, 26.12, 26.31, 32.61, 32.08, 36.58, 
      31.53, 42.84, 42.84, 42.84, 42.84, 31.68, 54.27, 30.26, 29.33, 
      29.33, 31.53, 32.66, 36.82), Task_Completion_Time = c(25L, 
      19L, 25L, 38L, 38L, 25L, 38L, 38L, 16L, 16L, 32L, 39L, 49L, 33L, 
      9L, 20L, 29L, 25L, 46L, 27L, 24L, 24L, 24L, 18L, 52L, 23L, 20L, 
      31L, 45L, 27L, 24L, 10L, 18L, 77L, 40L, 26L, 10L, 37L, 39L, 21L, 
      11L, 26L, 23L, 39L, 31L, 13L, 44L, 20L, 40L, 30L, 24L, 11L, 30L, 
      28L, 34L, 26L, 53L, 16L, 10L, 10L, 22L, 15L, 32L, 50L, 52L, 18L, 
      27L, 21L, 36L, 23L, 17L, 20L, 34L, 27L, 47L, 38L, 47L, 53L, 48L, 
      21L, 15L, 19L, 45L, 20L, 11L, 35L, 27L, 17L, 30L, 88L, 30L, 88L, 
      18L, 41L, 24L, 25L, 25L, 40L, 19L, 16L)), .Names = c("Age", 
      "BMI", "Task_Completion_Time"), class = c("data.table", 
      "data.frame"), row.names = c(NA, -100L))
  </code></pre>
  
  <p>I get an error</p>
  
  <pre><code>Error in function_list[[k]](value) : 
    could not find function "add_surface"
  </code></pre>
  
  <p>The best I could do was something like this below</p>
  
  <pre><code>plot_ly(z = as.numeric(test_plotly$Age), y = as.numeric(test_plotly$Task_Completion_Time), x = as.numeric(test_plotly$BMI))
  </code></pre>
  
  <p>But this is messy and nothing like the plotly surface plot examples.</p>
  
  <p><a href="https://i.stack.imgur.com/K2X3v.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/K2X3v.png" alt="enter image description here"></a></p>
  
  <p>Not sure what I am missing, any help on fixing this problem and producing a clean 3d surface plot is much appreciated.</p>