title: R Shiny Pass a vector as radioButtons choices argument
body: <p>I would like to define a radio button in Shiny which normally I could do for example as:</p>
  
  <pre><code>radioButtons("choose_country", h3("Country"),
               choices=c('uganda'='UG','tanzania'='TZ','kenya'='KE'))
  </code></pre>
  
  <p>Which gives the desired output:</p>
  
  <p>However, I would like the choices part of <code>radioButtons</code> to be read from an
  externally defined vector. i.e.</p>
  
  <pre><code>country_assg &lt;- c('uganda'='UG','tanzania'='TZ','kenya'='KE')
  </code></pre>
  
  <p>I would then like to paste this vector as follows:</p>
  
  <pre><code>radioButtons("choose_country", h3("Country"),
                 choices=country_assg)
  </code></pre>
  
  <p>This does not seem to work as it seems not to break up the elements in the <code>country_assg</code> vector as required.</p>
  
  <p>My question is how I can make <code>country_assg</code> to be evaluated as the choice argument inside the 
  <code>radioButtons</code> command so that I get the desired output.
  I would appreciate ideas to tackle the issue.</p>