title: Tidyquant: Getting trailing monthly return from each and every date (not just monthly)
body: <p>I'm trying to get the monthly percentage return from each day, not from every month. As you can see from the current output, it gets the monthly percentage return every month. </p>
  
  <pre><code>library(tidyquant)
  library(dplyr)
  
  df &lt;- c('AMZN','FB') %&gt;% 
    tq_get(get='stock.prices',
           from='1999-01-01',
           to=Sys.Date()) %&gt;%
    na.omit() %&gt;%
    group_by(symbol) %&gt;%
    tq_transmute(select=adjusted,
                 mutate_fun=periodReturn,
                 period='monthly',
                 col_rename='monthly.close') %&gt;%
    arrange(desc(date))
  </code></pre>
  
  <p>Current output:</p>
  
  <pre><code>symbol date monthly.close
  AMZN    2019-02-15  -0.0644545858       
  FB  2019-02-15  -0.0251364926       
  AMZN    2019-01-31  0.1443171389        
  FB  2019-01-31  0.2715692050        
  AMZN    2018-12-31  -0.1113497862       
  FB  2018-12-31  -0.0677050347       
  AMZN    2018-11-30  0.0576717501
  </code></pre>
  
  <p>Expected output</p>
  
  <pre><code>symbol date monthly.close
  AMZN    2019-02-15  ...
  FB  2019-02-15  ...
  AMZN    2019-02-14  ...
  FB  2019-02-14  ...
  AMZN    2019-02-13  ...
  FB  2019-02-13  ...
  AMZN    2019-02-12  ...
  [...]
  </code></pre>