title: Shiny - Source a R file,extract values and set input sliders according to the extracted values
body: <p>Fresh to shiny...<br>
   1. I want to create an <code>ui.R</code> using <code>dashboardPage</code> and define a <code>selectInput</code> box (Done!)<br>
   2. As soon as the user will selects one of the fields in the <code>selectInput</code>, a <code>Schools_Info.R</code> file would be sourced.
      I have tried <code>source("Schools_Info.R")</code> but I want some function which will run <code>Schools_Info.R</code> in backgroud.<br>
  How you do that?<br>
   3. <code>Schools_Info.R</code> contains values that I want to use as the <code>min</code> and <code>max</code> of a
  <code>sliderInput</code>.<br>
  How can I define <code>sliderInput</code> that will adjust its limits(<code>min</code> and <code>max</code>) automatically according to whatever the user selects from <code>selectInput</code> box?</p>
  
  <h2>ui.R</h2>
  
  <pre><code>library(shiny)
  options(shiny.trace=TRUE)
  library(shinydashboard)
  
  locations &lt;- c("Select your location",
             paste0("\tLocation1"),
             paste0("\tLocation2"),               
             paste0("\tLocation3")
             )
  
  
  ui &lt;- dashboardPage(
    dashboardHeader(title = "Basic dashboard"),
      dashboardSidebar(
            selectInput("selectedLoc",choices = locations),
            source("Schools_Info.R"),
            sliderInput("slider", "Number of observations:", 1, min, max)),
      dashboardBody(
        fluidRow(
  
        box(
          title = "Controls",
        )
      )
    )
  )
  </code></pre>