title: Plotly plot doesn't show up when using shiny
body: <p>I am trying to plot a plotly heatmap with a slider. The slider shows up but the plotly heatmap does not. When not used with shiny the heatmap plots just fine. At one point I got the code to work but I have since broken it and I don't know how. </p>
  
  <pre><code>library(gplots)
  library(plotly)
  library(shiny)
  
  
  #Ui
  ui &lt;- fluidPage(
  titlePanel("Example"),
  sidebarLayout(
  sidebarPanel(
  sliderInput(inputId = "P4Volume",
                label = "Example:",
                min = 50000,
                max = 1200000,
                value = 30)
  ),
  mainPanel(
      plotlyOutput(outputId = "heatmap"),
  )
  )
  )
  
  #Server
  server &lt;- function(input, output) {
  output$heatmap &lt;- renderPlotly({
  
  *Code here that takes input$P4Volume and creates a matrix z
  
  plot_ly(z,x,y,type= "heatmap",width=800,height=600)
  })
  }
  shinyApp(ui, server)
  </code></pre>
  
  <p>I've even tried a very simple example without the slider and just the plotly plot:</p>
  
  <pre><code>library(shiny)
  library(plotly)
  
  x=seq(0,10,2)
  y=seq(0,10,2)
  z=matrix(100,nrow=6,ncol=6)
  p=plot_ly(z=z, x = x, y =y,type="heatmap")
  
  ui &lt;- fluidPage(
  plotlyOutput("plot")
  )
  
  server &lt;- function(input, output) {
  output$plot &lt;- renderPlotly({p})
  }
  shinyApp(ui, server)
  </code></pre>
  
  <p>And I still don't get a plotly heatmap but when i plot it outside of shinny it plots fine...</p>