title: Long to wide data. Pandas
body: <p>I'm trying to take my dataframe from a long format in which I have a column with a categorical variable, into a wide format in which each category has it's own price column. Currently, my data looks like this:</p>
  
  <pre><code>date-time            date       vendor    payment_type   price
  03-10-15 10:00:00    03-10-15     A1            1          50
  03-10-15 10:00:00    03-10-15     A1            2          60
  03-10-15 10:00:00    03-11-15     A1            1          45
  03-10-15 10:00:00    03-11-15     A1            2          70
  03-10-15 10:00:00    03-12-15     B1            1          40
  03-10-15 10:00:00    03-12-15     B1            2          45
  03-10-15 10:00:00    03-10-15     C1            1          60
  03-10-15 10:00:00    03-10-15     C1            1          65
  </code></pre>
  
  <p>My goal is to have a column for every vendor's price and for each payment type and one row per day. When there are multiple values per day, I want to use the maximum value. The end result should look something like this.</p>
  
  <pre><code>Date       A1_Pay1   A2_Pay2 ... C1_Pay1   C1_Pay2
  03-10-15     50        60    ...   65        NaN
  03-11-15     45        70    ...   NaN       NaN
  03-12-15     NaN       NaN   ...   NaN       NaN
  </code></pre>
  
  <p>I tried using unstack and pivot, but I either wasn't getting what I was going for, or was getting an error about Date not being a unique index.</p>
  
  <p>Any ideas?</p>