Add plotylimited option to control vertical scaling locking on data plots

mementum · mementum · commit b4676008ca89 · 2017-06-02T23:57:09.000+02:00
diff --git a/backtrader/dataseries.py b/backtrader/dataseries.py
@@ -58,7 +58,7 @@ def TName(cls, tframe):
 
 
 class DataSeries(LineSeries):
-    plotinfo = dict(plot=True, plotind=True)
+    plotinfo = dict(plot=True, plotind=True, plotylimited=True)
 
     _name = ''
     _compression = 1
diff --git a/backtrader/plot/plot.py b/backtrader/plot/plot.py
@@ -684,7 +684,9 @@ def plotdata(self, data, indicators):
 
         ax.yaxis.set_major_locator(mticker.MaxNLocator(prune='both'))
         # make sure "over" indicators do not change our scale
-        ax.set_ylim(ax.get_ylim())
+        if data.plotinfo._get('plotylimited', True):
+            if axdatamaster is None:
+                ax.set_ylim(ax.get_ylim())
 
         if self.pinf.sch.volume:
             # if not self.pinf.sch.voloverlay:
diff --git a/docs2/plotting/plotting.rst b/docs2/plotting/plotting.rst
@@ -109,7 +109,9 @@ These are controlled by this data set in *Indicators* and *Observers*::
                     plotyticks=[],
                     plothlines=[],
                     plotforce=False,
-                    plotmaster=None,)
+                    plotmaster=None,
+		    plotylimited=True,
+               )
 
 Although ``plotinfo`` is shown as a ``dict`` during class definition, the
 metaclass machinery of *backtrader* turns that into an object which is
@@ -223,6 +225,17 @@ The meaning of the options
     **Monthly** data but is meant for **Daily** data. It only makes sense to
     plot it on the *daily* data which is where the indicator makes sense.
 
+  - ``plotylimited``: currently only applies to data feeds. If ``True``
+    (default), other lines on the data plot don't change the scale. Example:
+    Bollinger Bands (top and bottom) may be far away from the actual absolute
+    minimum/maximum of the data feed. With ```plotlimited=True``, those bands
+    remain out of the chart, because the data controls the scaling. If set to
+    ``False``, the bands affects the y-scale and become visible on the chart
+
+    A use case is the ``PivotPoint`` indicator which is calculated on
+    **Monthly** data but is meant for **Daily** data. It only makes sense to
+    plot it on the *daily* data which is where the indicator makes sense.
+
 
 Line specific plotting options
 ==============================
