title: developing interactive app using shiny and highcharter
body: <p>I'm trying to make a simple app with R using shiny that only has a highchart changing with the given parameter through slidebar.
  I've looked through web, but there aren't any clear tutorial or simple example that I can compare my code with it.
  So here's my code:</p>
  
  <pre><code>library(shiny)
  library(highcharter)
  library(dplyr)
  
  sigene_all = read_csv("res/significant_genes.csv")
  
  ui &lt;- fluidPage(
    titlePanel("Interactive Heatmap"),
    sidebarLayout(
      sidebarPanel(sliderInput(inputId = "slider", label = "Number of Cancers", min = 1, max = 12, value = 9)),
      mainPanel(highchartOutput("heatmap"))
    )
  )
  
  server &lt;- function(input, output) {
    output$heatmap &lt;- renderChart({
      hchart(sigene_all %&gt;% filter(count &gt;= input$slider),
             type = "heatmap", hcaes(x = gene, y = cancer_type, value = sgnf), name = "sgnf") %&gt;% 
        hc_add_theme(hc_theme_darkunica())
    })
  }
  
  shinyApp(ui = ui, server = server)
  </code></pre>
  
  <p>and this is the error that I get when I run the app:</p>
  
  <blockquote>
    <p>Warning: Error in server: could not find function "renderChart"
      52: server [&lt;..>/CTI/app.R#23]
    Error in server(...) : could not find function "renderChart"</p>
  </blockquote>
  
  <p>I've been searching but I haven't found anything related. I'd appreciate it if you help me with this simple code.</p>