title: No applicable method for 'mutate_' applied to an object of class "logical"
body: <p>I have a list of stock tickers in a vector form:</p>
  
  <pre><code>&gt; MSCI_USA
    [1] "SLB"   "NOV"   "BKR"   "HAL"   "XOM"   "VLO"   "OXY"   "WMB" 
    [9] "PXD"   "OKE"   "CVX"   "MRO"   "TRGP"  "HES"   "FANG"  "COP"
    .
    .
    .
    [681] "JLL"   "CBRE" 
  </code></pre>
  
  <p>And I created a function to read the tickers, load their stock prices and mutate the symbols to the data frame:</p>
  
  <pre><code>get_prices = function(ticker){
    df = tq_get(ticker, from = date) %&gt;% mutate(symbol = rep(ticker, length(date)))
  }
  </code></pre>
  
  <p>Lastly, the function <code>map()</code> is used to iterate over the items in <code>MSCI_USA</code> to get their stock prices and bind the resulting data frame for every stock in one single data frame using <code>bind_rows()</code>:</p>
  
  <pre><code>tickers_df = map(MSCI_USA, get_prices) %&gt;% bind_rows()
  </code></pre>
  
  <p>Problem:</p>
  
  <p>R returned an error:</p>
  
  <pre><code>Error in UseMethod("mutate_") : 
    no applicable method for 'mutate_' applied to an object of class "logical"
  </code></pre>
  
  <p>I am not sure what is the error meant and need help to resolve this one. Thanks in advance!</p>