title: R, using 'fPortfolio' package: setting the risk free interest rate
body: <p>I am struggling with the 'fPortfolio' package in R. 
  I need to set the risk free interest rate. (obviously I need this for when the sharpe ratio etc are calculated; but an arbitrary risk-free rate of is assumed) 
  I have tried:</p>
  
  <p>-Attempt 1</p>
  
  <pre><code>Spec = portfolioSpec()[[1]]  
  # Change Risk Free Rate
  setRiskFreeRate(Spec) = 0.008
  Frontier = portfolioFrontier(returns_ts,spec = Spec)
  weightsSlider(Frontier)
  </code></pre>
  
  <p>-Attempt 2</p>
  
  <pre><code>weightsSlider(Frontier,spec=Spec)
  </code></pre>
  
  <p>-Attempt 3</p>
  
  <pre><code>weightsSlider(Frontier,spec=Spec,riskFreeRate = 0.008)
  </code></pre>
  
  <p>-Problem, each time, there is no error produced. In fact, if i call the 'Spec' object it informs me of a 0.08 rf interest rate. HOWEVER; when I look at the sharpe ratio; it is the tangent line to the frontier, drawn from a completely arbitrary target return. </p>