title: ValueError: Could not interpret input in seaborn
body: <p>I have this data frame:</p>
  <pre><code>df = {'DATE':  [43390, 43599, 43605, 43329, 43440],
        'STORE': [1, 1, 1, 2, 2],
        'LYLTY_CARD_NBR': [1000, 1307, 1343, 2373, 2426],
        'TXN_ID': [1, 348, 383, 974, 1038],
        'PROD_QTY': [2, 3, 2, 5, 3],
        'TOT_SALES': [6.0, 6.3, 2.9, 15.0, 13.8]}
  
  transac = pd.DataFrame(df)
  
      DATE    STORE   LYLTY_CARD_NBR  TXN_ID  PROD_QTY    TOT_SALES
  0   43390   1         1000             1           2    6.0
  1   43599   1         1307             348         3    6.3
  2   43605   1         1343             383         2    2.9
  3   43329   2         2373             974         5    15.0
  4   43440   2         2426             1038        3    13.8
  </code></pre>
  <p>When I try to plot a boxplot from seaborn of the TOT_SALES column I get this error. The type of the column is float64. I tried the same with matplotlib and it worked but not with seaborn:</p>
  <pre><code>sns.boxplot(y='TOT_SALES', df=transac)
  
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-16-29f35d075db2&gt; in &lt;module&gt;
  ----&gt; 1 sns.boxplot(y='TOT_SALES', df=transac)
  
  ~\Anaconda3\lib\site-packages\seaborn\categorical.py in boxplot(x, y, hue, data, order, hue_order, orient, color, palette, saturation, width, dodge, fliersize, linewidth, whis, ax, **kwargs)
     2239     plotter = _BoxPlotter(x, y, hue, data, order, hue_order,
     2240                           orient, color, palette, saturation,
  -&gt; 2241                           width, dodge, fliersize, linewidth)
     2242 
     2243     if ax is None:
  
  ~\Anaconda3\lib\site-packages\seaborn\categorical.py in __init__(self, x, y, hue, data, order, hue_order, orient, color, palette, saturation, width, dodge, fliersize, linewidth)
      441                  width, dodge, fliersize, linewidth):
      442 
  --&gt; 443         self.establish_variables(x, y, hue, data, orient, order, hue_order)
      444         self.establish_colors(color, palette, saturation)
      445 
  
  ~\Anaconda3\lib\site-packages\seaborn\categorical.py in establish_variables(self, x, y, hue, data, orient, order, hue_order, units)
      150                 if isinstance(var, str):
      151                     err = &quot;Could not interpret input '{}'&quot;.format(var)
  --&gt; 152                     raise ValueError(err)
      153 
      154             # Figure out the plotting orientation
  
  ValueError: Could not interpret input 'TOT_SALES'
  </code></pre>
  <p>Where is the problem?</p>