add ability to shift moving average on plots

src/mplfinance/_arg_validators.py

@@ -103,22 +103,45 @@ def _get_valid_plot_types(plottype=None):
 
 
 def _mav_validator(mav_value):
-    ''' 
+    '''
     Value for mav (moving average) keyword may be:
-    scalar int greater than 1, or tuple of ints, or list of ints (greater than 1).
-    tuple or list limited to length of 7 moving averages (to keep the plot clean).
+    scalar int greater than 1, or tuple of ints, or list of ints (each greater than 1)
+    or a dict of `period` and `shift` each of which may be:
+    scalar int, or tuple of ints, or list of ints: each `period` int must be greater than 1
     '''
-    if isinstance(mav_value,int) and mav_value > 1:
+    def _valid_mav(value, is_period=True):
+        if not isinstance(value,(tuple,list,int)):
+            return False
+        if isinstance(value,int):
+            return (value >= 2 or not is_period)
+        # Must be a tuple or list here:
+        for num in value:
+            if not isinstance(num,int) or (is_period and num < 2):
+                return False
         return True
-    elif not isinstance(mav_value,tuple) and not isinstance(mav_value,list):
+
+    if not isinstance(mav_value,(tuple,list,int,dict)):
         return False
 
-    if not len(mav_value) < 8:
+    if not isinstance(mav_value,dict):
+        return _valid_mav(mav_value)
+
+    else: #isinstance(mav_value,dict)
+        if 'period' not in mav_value: return False
+
+        period = mav_value['period']
+        if not _valid_mav(period): return False
+
+        if 'shift' not in mav_value: return True
+
+        shift  = mav_value['shift']
+        if not _valid_mav(shift, False):  return False
+        if isinstance(period,int) and isinstance(shift,int): return True
+        if isinstance(period,(tuple,list)) and isinstance(shift,(tuple,list)):
+            if len(period) != len(shift): return False
+            return True
         return False
-    for num in mav_value:
-        if not isinstance(num,int) and num > 1:
-            return False
-    return True
+
 
 def _hlines_validator(value):
     if isinstance(value,dict):

src/mplfinance/_version.py

@@ -1,5 +1,5 @@
 
-version_info = (0, 12, 7, 'alpha', 17)
+version_info = (0, 12, 7, 'alpha', 18)
 
 _specifier_ = {'alpha': 'a','beta': 'b','candidate': 'rc','final': ''}
 

src/mplfinance/plotting.py

@@ -978,8 +978,12 @@ def _plot_mav(ax,config,xdates,prices,apmav=None,apwidth=None):
         mavgs = config['mav']
     mavp_list = []
     if mavgs is not None:
+        shift = None
+        if isinstance(mavgs,dict):
+            shift = mavgs['shift']
+            mavgs = mavgs['period']
         if isinstance(mavgs,int):
-            mavgs = mavgs,      # convert to tuple 
+            mavgs = mavgs,      # convert to tuple
         if len(mavgs) > 7:
             mavgs = mavgs[0:7]  # take at most 7
 
@@ -988,8 +992,11 @@ def _plot_mav(ax,config,xdates,prices,apmav=None,apwidth=None):
         else:
             mavc = None
 
-        for mav in mavgs:
-            mavprices = pd.Series(prices).rolling(mav).mean().values
+        for idx,mav in enumerate(mavgs):
+            mean = pd.Series(prices).rolling(mav).mean()
+            if shift is not None:
+                mean = mean.shift(periods=shift[idx])
+            mavprices = mean.values
             lw = config['_width_config']['line_width']
             if mavc:
                 ax.plot(xdates, mavprices, linewidth=lw, color=next(mavc))

tests/test_addplot.py

@@ -354,3 +354,23 @@ def test_addplot11(bolldata):
         print('result=',result)
     assert result is None
 
+def test_addplot12(bolldata):
+
+    df = bolldata
+
+    fname = base+'12.png'
+    tname = os.path.join(tdir,fname)
+    rname = os.path.join(refd,fname)
+
+    mpf.plot(df,type='candle',volume=True,savefig=tname,mav={'period':(20,40,60), 'shift': [5,10,20]})
+
+    tsize = os.path.getsize(tname)
+    print(glob.glob(tname),'[',tsize,'bytes',']')
+
+    rsize = os.path.getsize(rname)
+    print(glob.glob(rname),'[',rsize,'bytes',']')
+
+    result = compare_images(rname,tname,tol=IMGCOMP_TOLERANCE)
+    if result is not None:
+       print('result=',result)
+    assert result is None