3d surface example (#1974)

Author: emmanuelle

doc/python/3d-surface-plots.md

@@ -52,6 +52,27 @@ fig.update_layout(title='Mt Bruno Elevation', autosize=False,
 fig.show()
 ```
 
+### Passing x and y data to 3D Surface Plot
+
+If you do not specify `x` and `y` coordinates, integer indices are used for the `x` and `y` axis. You can also pass `x` and `y` values to `go.Surface`. 
+
+```python
+import plotly.graph_objects as go
+import pandas as pd
+import numpy as np
+# Read data from a csv
+z_data = pd.read_csv('https://raw.githubusercontent.com/plotly/datasets/master/api_docs/mt_bruno_elevation.csv')
+z = z_data.values
+sh_0, sh_1 = z.shape
+x, y = np.linspace(0, 1, sh_0), np.linspace(0, 1, sh_1)
+fig = go.Figure(data=[go.Surface(z=z, x=x, y=y)])
+fig.update_layout(title='Mt Bruno Elevation', autosize=False,
+                  width=500, height=500,
+                  margin=dict(l=65, r=50, b=65, t=90))
+fig.show()
+```
+
+
 #### Surface Plot With Contours