title: special character in function argument within Shiny app
body: <p>Inside the UI part of a Shiny app i have the following:</p>
  <pre><code>sliderInput(&quot;cvn&quot;,&quot;Enter the cv training n number:&quot;,min = 1,
                              max = 20,
                              value = cvnumber,step = 1)
  </code></pre>
  <p>Then within the server part of the same shiny app i want to call a function and pass the <code>input$cvn</code> as an argument as in the following lines:</p>
  <pre><code>funcfit_cart &lt;- function( input$cvn ){
          set.seed(123)
          fit.cart &lt;- train(as.formula(paste(input$var ,  &quot; ~ .&quot;)),
          data = gyno_train(), method=&quot;rpart&quot;, metric=metric, trControl=trainControl(method=&quot;cv&quot;, number=cvnumber))
          return(fit.cart)
      }
  </code></pre>
  <p>As i try to do this i get the red x error flag message:</p>
  <pre><code>unexpected token 'input', expected 'RPAREN'
  unexpected closing bracket 'input'
  unmatched opening bracket '('
  missing function definition
  unexpected token '$'
  unexpected token ')'
  </code></pre>
  <p>Do you know how i can insert within the function argument the call to the <code>input$cvn</code> ?</p>