title: Multiple linestyles with seaborn.facetgrid
body: <p>I have data in a tidy ('long form') pandas.DataFrame looking like this (shortened) :</p>
  
  <pre><code>    dataset  limit type_long type  distance  count  frequency
  0       pos     -1      DR-3   DR        -3     17   0.005866
  1       pos     -1      DR-2   DR        -2     70   0.024155
  2       pos     -1      DR-1   DR        -1    124   0.04278
  ...     ...     ...     ...    ...       ...   ...    ...
  810     neg    -10       DR9   DR         9    435   0.033565
  811     neg    -10      DR10   DR        10    432   0.033333
  812     neg    -10      IR-3   IR        -3    260   0.02006
  </code></pre>
  
  <p>I almost managed to represent the data as I intended: </p>
  
  <p>1 subplot per 'type' with x and y being 'distance' and 'frequency' respectively and separating the 'pos' and 'neg' datasets by using continuous and dashed lines.
  My code is here:</p>
  
  <pre><code>grid = sns.FacetGrid(df, col = 'type', hue= 'limit', legend_out = True) 
  grid.map(sns.pointplot, 'distance', 'frequency', 'dataset', linestyles = ['-', ':'], markers=['','']).set_titles('{col_name}')
  grid.add_legend()
  plt.show()
  </code></pre>
  
  <p>Which gives a fairly ugly output: the 'pos' dataset appears transparent and the legend disapeared (I cannot post an image, sorry)</p>
  
  <p>I don't understand the strange behaviour of pointplot in this case. Is there a way correct the transparency? Or maybe a better approach to create this figure.</p>
  
  <p>For the legend I guess this is a conflict between the two hue definitions. Is there a way to display a double legend with colors for the limits and linestyle for the dataset ?</p>
  
  <p>I've made a minimal working example with seaborn datasets, the graphs are awfull but it shows the problem well:</p>
  
  <pre><code>import seaborn as sns
  
  titanic = sns.load_dataset('titanic')
  sns.set(style="ticks")
  grid = sns.FacetGrid(titanic, col = 'class', hue= 'embark_town', legend_out = True) 
  grid.map(sns.pointplot, 'fare', 'age', 'sex', linestyles = ['-', ':'], markers=['',''])
  grid.add_legend() 
  </code></pre>