add a 4th example to create_quiver to showcase the new param.

Author: dabana

Diff for: plotly/figure_factory/_quiver.py

@@ -83,6 +83,29 @@ def create_quiver(x, y, u, v, scale=.1, arrow_scale=.3,
     # Add title to layout
     fig['layout'].update(title='Quiver Plot')
 
+    # Plot
+    py.plot(fig, filename='quiver')
+    ```
+
+    Example 4: Forcing a fix scale ratio to maintain the arrow length
+    ```
+    import plotly.plotly as py
+    from plotly.figure_factory import create_quiver
+
+    import numpy as np
+
+    # Add data
+    x,y = np.meshgrid(np.arange(0.5, 3.5, .5), np.arange(0.5, 4.5, .5))
+    u = x
+    v = y
+    angle = np.arctan(v / u)
+    norm = 0.25
+    u = norm * np.cos(angle)
+    v = norm * np.sin(angle)
+
+    # Create quiver with a fix scale ratio
+    fig = create_quiver(x, y, u, v, scale = 0.75, scaleratio = 0.5)
+
     # Plot
     py.plot(fig, filename='quiver')
     ```