title: Year/Quarter to datetime datatype
body: <p>I am trying to convert the "Year_Quarter" column (object) to datetime64 datatype.Note there is a space between year and quarter.</p>
  
  <pre><code>          df
                   Year_Quarter
               0     2009 Q1
               1     2009 Q1
               2     2009 Q2
  </code></pre>
  
  <p>I tried the code below</p>
  
  <pre><code>       df['Year_Quarter']=pd.to_datetime(df['Year_Quarter'].str.replace(' ', ''))+pd.offsets.QuarterBegin(startingMonth=1)
  </code></pre>
  
  <p>However, I got the following error:</p>
  
  <pre><code>      AttributeError: Can only use .str accessor with string values!
  </code></pre>
  
  <p>Thank you for your help!</p>