Feature Request: Ability to plot step /staircase lines implemented Issue #367

Author: instrat

src/mplfinance/plotting.py

@@ -909,6 +909,13 @@ def _addplot_columns(panid,panels,ydata,apdict,xdates,config):
         width  = apdict['width'] if apdict['width'] is not None else 1.6*config['_width_config']['line_width']
         alpha  = apdict['alpha']
         ax.plot(xdates,ydata,linestyle=ls,color=color,linewidth=width,alpha=alpha)
+    elif aptype == 'step':
+        where = apdict['where']
+        ls = apdict['linestyle']
+        color  = apdict['color']
+        width  = apdict['width'] if apdict['width'] is not None else 1.6*config['_width_config']['line_width']
+        alpha  = apdict['alpha']
+        ax.step(range(len(xdates)),ydata,where = where,linestyle=ls,color=color,linewidth=width,alpha=alpha)
     else:
         raise ValueError('addplot type "'+str(aptype)+'" NOT yet supported.')
 
@@ -995,7 +1002,8 @@ def _auto_secondary_y( panels, panid, ylo, yhi ):
 def _valid_addplot_kwargs():
 
     valid_linestyles = ('-','solid','--','dashed','-.','dashdot','.','dotted',None,' ','')
-    valid_types = ('line','scatter','bar', 'ohlc', 'candle')
+    valid_types = ('line','scatter','bar', 'ohlc', 'candle','step')
+    valid_wheres = ('pre','post','mid')
 
     vkwargs = {
         'scatter'     : { 'Default'     : False,
@@ -1055,6 +1063,9 @@ def _valid_addplot_kwargs():
 
         'yscale'      : { 'Default'     : None,
                           'Validator'   : lambda value: _yscale_validator(value) },
+
+        'where'      : { 'Default'     : 'pre',
+                          'Validator'   : lambda value : value in valid_wheres },                  
     }
 
     _validate_vkwargs_dict(vkwargs)