title: How to delete an portfolio after using initPortf in package "blotter" in R
body: <p>When using the function <code>initPortf</code> to initialize portfolio in package <code>blotter</code> in R,
  we can initialize a portfolio, such as:</p>
  
  <pre><code>currency("USD")
  stock("SPY",currency="USD",multiplier=1)
  b.strategy &lt;- "bFaber"
  initPortf(b.strategy,'SPY', initDate='1997-12-31') 
  </code></pre>
  
  <p>But when we want to initialize the portfolio again, we must delete the portfolio b.strategy first:</p>
  
  <pre><code>initPortf(b.strategy, "SPY", initDate = "1997-12-31") : 
  Portfolio bFaber already exists, use updatePortf() or addPortfInstr() to update it.
  </code></pre>
  
  <p>the <code>rm()</code> could not be used here, when I need to delete it, I have to clear all of the workspace. Is there any function to delete it?</p>