title: Error in RShiny ui.r argument missing
body: <p>Trying to create a ui.r file for plotting a logistic regression with the following features:</p>
  
  <p>selecting inputs (y-variable: breakdown, x-variables: Temperature, Humidity, Hours) and variable range slider. </p>
  
  <p>I got the following error: <code>Error in tag("div", list(...)) : argument is missing, with no default</code></p>
  
  <pre><code>require(shiny)    
  shinyUI(pageWithSidebar(
    headerPanel("Home Automation Data Model - TV"),      
    sidebarPanel(
      wellPanel(
        selectInput(
          inputId = "x_var",
          label = "X variable",
          choices = c(
            "Temperature (Celcius)" = "Temp",
            "Humidity (Percentage)" = "Hum",
            "Hours" = "Hrs"
          ),
          selected = "Temperature"
        ),
  
        uiOutput("x_range_slider")
      ),      
  
      wellPanel(
        selectInput(
          inputId = "y_var",
          label = "Y variable",
          choices = c("Breakdowns (Yes/No)" = "y"),
        ),
  
        uiOutput("y_range_slider")
      ),        
  
      wellPanel(
        p(strong("Model predictions")),
        checkboxInput(inputId = "mod_logistic",    label = "Logistic (dot-dash)"),
        conditionalPanel(
          condition = "input.mod_loess == true",
          sliderInput(
            inputId = "mod_loess_span",
            label = "Smoothing (alpha)",
            min = 0.15,
            max = 1,
            step = 0.05,
            value = 0.75
          )
        )
      )
    ),
  
    mainPanel(
      plotOutput(outputId = "main_plot"),        
      conditionalPanel(
        "input.mod_logistic == true",
        p(strong("Logit model")),
        verbatimTextOutput(outputId = "mod_logistic_text")
      ),
    )      
  ))
  </code></pre>
  
  <blockquote>
    <p>Error in tag("div", list(...)):argument is missing, with no default</p>
  </blockquote>