add demo_gridspec06.py and update gridspec doc (original patch from Paul Ivanov)

svn path=/trunk/matplotlib/; revision=8916

Author: leejjoon

doc/users/gridspec.rst

@@ -129,6 +129,16 @@ parameters are set to that of the location of the given SubplotSpec. ::
 .. plot:: users/plotting/examples/demo_gridspec04.py
 
 
+A Complex Nested GridSpec using SubplotSpec
+===========================================
+
+Here's a more sophisticated example of nested gridspec where we put
+a box around each cell of the outer 4x4 grid, by hiding appropriate 
+spines in each of the inner 3x3 grids. ::
+
+.. plot:: users/plotting/examples/demo_gridspec06.py
+
+
 GridSpec with Varying Cell Sizes
 ================================
 

doc/users/plotting/examples/demo_gridspec06.py

@@ -0,0 +1,53 @@
+import matplotlib.pyplot as plt
+import matplotlib.gridspec as gridspec
+import numpy as np
+
+try:
+    from itertools import product
+except ImportError:
+    # product is new in v 2.6
+    def product(*args, **kwds):
+        pools = map(tuple, args) * kwds.get('repeat', 1)
+        result = [[]]
+        for pool in pools:
+            result = [x+[y] for x in result for y in pool]
+        for prod in result:
+            yield tuple(prod)
+
+
+def squiggle_xy(a, b, c, d, i=np.arange(0.0, 2*np.pi, 0.05)):
+    return np.sin(i*a)*np.cos(i*b), np.sin(i*c)*np.cos(i*d)
+
+f = plt.figure(figsize=(8, 8))
+
+# gridspec inside gridspec
+outer_grid = gridspec.GridSpec(4, 4, wspace=0.0, hspace=0.0)
+
+for i in xrange(16):
+    inner_grid = gridspec.GridSpecFromSubplotSpec(3, 3,
+            subplot_spec=outer_grid[i], wspace=0.0, hspace=0.0)
+    a, b = int(i/4)+1,i%4+1
+    for j, (c, d) in enumerate(product(range(1, 4), repeat=2)):
+        ax = plt.Subplot(f, inner_grid[j])
+        ax.plot(*squiggle_xy(a, b, c, d))
+        ax.set_xticks([])
+        ax.set_yticks([])
+        f.add_subplot(ax)
+
+all_axes = f.get_axes()
+
+#show only the outside spines
+for ax in all_axes:
+    for sp in ax.spines.values():
+        sp.set_visible(False)
+    if ax.is_first_row():
+        ax.spines['top'].set_visible(True)
+    if ax.is_last_row():
+        ax.spines['bottom'].set_visible(True)
+    if ax.is_first_col():
+        ax.spines['left'].set_visible(True)
+    if ax.is_last_col():
+        ax.spines['right'].set_visible(True)
+
+plt.show()
+