title: R plotly(): hovertemplate formatting
body: <p>I'm plotting a line graph and need help designing the hover template. I think it should be very easy, but unfortunately I can't figure it out myself.</p>
  <p>This is the code for plotting my graph:</p>
  <pre><code> p &lt;- plot_ly(dt.dataSpread, x = ~dt.dataSpread$date, y = ~dt.dataSpread$priceDifference, 
                mode = 'lines', type = 'scatter', line = list(color = &quot;#007d3c&quot;),
                text = ~product1, connectgaps = TRUE,
                hovertemplate = paste(&quot;&lt;b&gt;%{text} - 'product2??'&lt;/b&gt;&lt;br&gt;&quot;,
                                      &quot;%{xaxis.title.text}:  %{x}&lt;br&gt;&quot;,
                                      &quot;%{yaxis.title.text}:  %{y}&lt;br&gt;&lt;extra&gt;&lt;/extra&gt;&quot;)) %&gt;%
                layout(title = &quot;&lt;b&gt;Price Difference SPREAD&quot;, xaxis = list(title = &quot;Date&quot;), 
                       yaxis = list(title = &quot;EUR/MWh&quot;), showlegend = FALSE) %&gt;%
                                
  </code></pre>
  <p>And the plot of the graph looks like this: <a href="https://i.stack.imgur.com/PtOOl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PtOOl.png" alt="Hovertemplate-PLOT" /></a></p>
  <p>I need help with the <strong>red underlined</strong> part. At the beginning I define two products (strings), but they are not always the same, here e.g.: <code>product1 &lt;- &quot;EEX ATB Cal-2020&quot;</code> and <code>product2 &lt;- &quot;PEGAS Cal-2020&quot;</code>.</p>
  <p>As you can see, I have already defined the first product in the code with <code>text = ~ product1</code> and as a text output in the hovertemplate. But unfortunately I can't handle it for <code>product2</code>.</p>
  <p>Does anyone know how this could work?</p>