matplotlib
diff --git a/‎examples/lines_bars_and_markers/AngleArc.py
+64 b/‎examples/lines_bars_and_markers/AngleArc.py
+64
diff --git a/‎examples/lines_bars_and_markers/angle_arc.py
-95 b/‎examples/lines_bars_and_markers/angle_arc.py
-95
@@ -0,0 +1,64 @@
+import numpy as np
+import matplotlib.pyplot as plt
+from matplotlib.patches import Arc
+from matplotlib.transforms import IdentityTransform
+
+class AngleArc(Arc):
+    def __init__(self, xy, vec1, vec2, size=100, units="pixels", ax=None, fig=None, **kwargs):
+        self._xydata = xy # in data coordinates
+        self.ax = ax or plt.gca()
+        self.fig = fig or plt.gcf()
+        self.vec1 = vec1 # tuple or array of coordinates, relative to xy
+        self.vec2 = vec2 # tuple or array of coordinates, relative to xy
+        self.size = size
+
+        super().__init__(self._xydata, size, size, angle=0.0,
+                 theta1=self.theta1, theta2=self.theta2, **kwargs)
+        
+        self.set_transform(IdentityTransform())
+
+        if units == "relative":
+            fig.canvas.mpl_connect("resize_event", self._resize)
+
+        self.ax.add_patch(self)
+
+    def _resize(self, event):
+        x0, y0 = self.ax.transAxes.transform((0, 0))
+        x1, y1  = self.ax.transAxes.transform((1, 1))
+        dx = x1 - x0
+        dy = y1 - y0
+        smallest = min(dx, dy)
+        self.width = 0.25*dx
+        self.height = 0.25*dx
+
+    def get_center_pixels(self):
+        """ return center in pixel coordinates """
+        return self.ax.transData.transform(self._xydata)
+    
+    def set_center(self, xy):
+        """ set center in data coordinates """
+        self._xydata = xy
+
+    _center = property(get_center_pixels, set_center)
+    
+    def get_theta(self, vec):
+        vec_in_pixels = self.ax.transData.transform(vec) - self._center
+        return np.rad2deg(np.arctan2(vec_in_pixels[1], vec_in_pixels[0]))
+        
+    def get_theta1(self):
+        return self.get_theta(self.vec1)
+        
+    def get_theta2(self):
+        return self.get_theta(self.vec2)
+        
+    def set_theta(self, angle):
+        pass
+         
+    theta1 = property(get_theta1, set_theta)
+    theta2 = property(get_theta2, set_theta)
+
+fig, ax = plt.subplots()
+
+ax.plot([2,.5,1],[0,.2,1])
+am = AngleArc((0.5, 0.2), (2, 0), (1, 1), size=100, units="relative", ax=ax, fig=fig)
+plt.show()