From c238be004ebb4a16917dc53cf5f53a6b52a4be1e Mon Sep 17 00:00:00 2001
From: Mikhail Terekhov <terekhov@emc.com>
Date: Thu, 15 Dec 2016 09:26:19 -0500
Subject: [PATCH 1/2] add test case for the PlotDataItem.clear() in stepMode

---
 pyqtgraph/graphicsItems/tests/test_PlotDataItem.py | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/pyqtgraph/graphicsItems/tests/test_PlotDataItem.py b/pyqtgraph/graphicsItems/tests/test_PlotDataItem.py
index 8851a0a2..b506a654 100644
--- a/pyqtgraph/graphicsItems/tests/test_PlotDataItem.py
+++ b/pyqtgraph/graphicsItems/tests/test_PlotDataItem.py
@@ -9,16 +9,16 @@ def test_fft():
     x = np.linspace(0, 1, 1000)
     y = np.sin(2 * np.pi * f * x)
     pd = pg.PlotDataItem(x, y)
-    pd.setFftMode(True)    
+    pd.setFftMode(True)
     x, y = pd.getData()
     assert abs(x[np.argmax(y)] - f) < 0.03
-    
+
     x = np.linspace(0, 1, 1001)
     y = np.sin(2 * np.pi * f * x)
     pd.setData(x, y)
     x, y = pd.getData()
     assert abs(x[np.argmax(y)]- f) < 0.03
-    
+
     pd.setLogMode(True, False)
     x, y = pd.getData()
     assert abs(x[np.argmax(y)] - np.log10(f)) < 0.01
@@ -58,3 +58,9 @@ def test_clear():
 
     assert pdi.xData == None
     assert pdi.yData == None
+
+def test_clear_in_step_mode():
+    w = pg.PlotWidget()
+    c = pg.PlotDataItem([1,4,2,3], [5,7,6], stepMode=True)
+    w.addItem(c)
+    c.clear()

From b13062f081464d6950990d7e3add969e43e7d934 Mon Sep 17 00:00:00 2001
From: Mikhail Terekhov <terekhov@emc.com>
Date: Wed, 14 Dec 2016 22:39:39 -0500
Subject: [PATCH 2/2] In PlotDataItem.clear() use corresponding curve.clear()
 and scatter.clear()

Otherwise when stepMode is True curve.setData([]) causes exception:
"len(X) must be len(Y)+1 ..."
---
 pyqtgraph/graphicsItems/PlotDataItem.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/pyqtgraph/graphicsItems/PlotDataItem.py b/pyqtgraph/graphicsItems/PlotDataItem.py
index 2faa9ac1..1bf48f5d 100644
--- a/pyqtgraph/graphicsItems/PlotDataItem.py
+++ b/pyqtgraph/graphicsItems/PlotDataItem.py
@@ -627,9 +627,9 @@ class PlotDataItem(GraphicsObject):
         #self.yClean = None
         self.xDisp = None
         self.yDisp = None
-        self.curve.setData([])
-        self.scatter.setData([])
-            
+        self.curve.clear()
+        self.scatter.clear()
+
     def appendData(self, *args, **kargs):
         pass