title: plotly bar and line chart
body: <p>I want to plot a bar together with a line chart in R with plotly.</p>
  
  <p>My first attempt was</p>
  
  <pre><code>p &lt;- plot_ly(
    x = c(1,2,3,4,5),
    y = c(1,2,1.5,3,2),
    type='scatter',
    mode='lines',
    line = list(color = 'black')
  )
  add_trace(
    p,
    x = c(1,2,3,4,5),
    y = c(0.5,0.7,0.6,0.9,0.8),
    type='bar',
    marker = list(color = 'red')
  )
  </code></pre>
  
  <p>The result is right, but I get the following warning:</p>
  
  <blockquote>
    <p>Warning message: The following attributes don't exist: 'mode', 'line'</p>
  </blockquote>
  
  <p>I guess cause the bar plot in <code>add_trace()</code> cannot handle the <code>line</code> and <code>mode</code> parameter from the <code>plot_ly()</code> function. So I changed the order:</p>
  
  <pre><code>p &lt;- plot_ly(
    x = c(1,2,3,4,5),
    y = c(0.5,0.7,0.6,0.9,0.8),
    type='bar',
    marker = list(color = 'red')
  )
  add_trace(
    p,
    x = c(1,2,3,4,5),
    y = c(1,2,1.5,3,2),
    type='scatter',
    mode='lines',
    line = list(color = 'black')
  )
  </code></pre>
  
  <p>This time I get the following message and red markers are displayed on the black line chart.</p>
  
  <blockquote>
    <p>A marker object has been specified, but markers is not in the mode
    Adding markers to the mode...</p>
  </blockquote>
  
  <p>How can I fix this? (I'm using the R package <em>plotly 4.1.0</em>)</p>