Create rot_rectangle.py

I added rot_rectangle.py to have an example showing the use of rotated rectangles (which I heavily used during my PhD to plot splitting parameters in map view).

Author: michaelgrund

examples/gallery/plot/rot_rectangle.py

@@ -0,0 +1,40 @@
+"""
+Rotated rectangle using azimuth
+----------------
+
+The :meth:`pygmt.Figure.plot` method can plot rotated rectangles based on a 
+given azimuth (in degrees east of north) as well as length and width. We can 
+define the required parameters in a numpy array or use an appropriately 
+formatted input file. Such representations are often used to e.g. display 
+results of shear-wave splitting analysis.
+"""
+
+import pygmt
+import numpy as np
+
+fig = pygmt.Figure()
+
+# generate a basemap around Big Island (Hawai'i) showing coastlines, land, and water
+fig.coast(
+    region = [-156.5, -154.5, 18.5, 20.5],
+    projection = "M6c",
+    land = "grey",
+    water = "lightblue",
+    shorelines = True,
+    resolution = "f",
+    frame=["x1", "y1"]
+)
+
+# store parameters for rotated rectangle in a numpy 
+# array (lon, lat, azimuth in degrees east of north, lenght, width)
+data = np.array([[-155.533, 19.757, 45, 60, 5]])
+
+# pass the data to the plotting function in addition to the corresponding 
+# style shortcut for rotated rectangles ("J") as well as set color and pen for 
+# the rectangle
+fig.plot(data = data,
+         style = "J",
+         color = "red3",
+         pen = "black")
+
+fig.show()