title: R plotly x axis character / factor (combination number and -). plot only showing axis that contain numbers only. bug?
body: <p>I am trying to use <code>plotly</code> to plot a bar chart with strings (combination number) as x-axis.<br>
  ("1", "2", "3", "4 - 5", "6 - 8","9 - 13", "14 - 21", "22 - 34", "35 - 55")</p>
  
  <p>However, Only 3 data is being ploted. ("1", "2", "3")</p>
  
  <p>Here is the code:</p>
  
  <pre><code>library(plotly)
  
  dfb = structure(groups = c("1", "2", "3", "4 - 5", "6 - 8",
                          "9 - 13", "14 - 21", "22 - 34", "35 - 55"),
      counts = c(29090,10074, 4573, 4029, 2289, 1120, 337, 78, 15)),
    class = c("data.frame"),
    row.names = c(NA,-9L),
    .Names = c("groups","counts")
  )
  
    plot_ly(dfb,
        x = groups,
        y = counts,
        type = "bar")
  </code></pre>
  
  <p>returns:</p>
  
  <p><a href="https://i.stack.imgur.com/UCupv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UCupv.png" alt="enter image description here"></a></p>
  
  <p>But if I filtered on of groups that contain only numbers, it is working well:</p>
  
  <pre><code>  dfc=subset(dfb,dfb$groups!='1')
    plot_ly(dfc,
        x = groups,
        y = counts,
        type = "bar")
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/rHXGB.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rHXGB.png" alt="enter image description here"></a></p>
  
  <p>Why is this happening?
  And how to solve this?</p>
  
  <p>I'm using plotly because I want to used it with Shiny, and for now it is the most fit for me.</p>
  
  <p>I didn't use ggplotly (make ggplot and then convert it to plotly) because sometimes axis tittle being cut off.</p>