Merge pull request #2106 from vighneshbirodkar/hm_doc

Improved region boundary RAG docs

doc/examples/segmentation/plot_boundary_merge.py

@@ -3,7 +3,15 @@
 Hierarchical Merging of Region Boundary RAGs
 ============================================
 
-TODO: Description
+This example demonstrates how to perform hierarchical merging on region
+boundary Region Adjacency Graphs (RAGs). Region boundary RAGs can be
+constructed with the :py:func:`skimage.future.graph.rag_boundary` function.
+The regions with the lowest edge weights are successively merged until there
+is no edge with weight less than ``thresh``. The hierarchical merging is done
+through the :py:func:`skimage.future.graph.merge_hierarchical` function.
+For an example of how to construct region boundary based RAGs, see
+:any:`plot_rag_boundary`.
+
 """
 
 from skimage import data, segmentation, filters, color

doc/examples/segmentation/plot_rag_boundary.py

@@ -3,8 +3,13 @@
 Region Boundary based RAGs
 ==========================
 
-This example demonstrates construction of region boundary based RAGs with the
-`rag_boundary` function.
+Construct a region boundary RAG with the ``rag_boundary`` function. The
+function  :py:func:`skimage.future.graph.rag_boundary` takes an
+``edge_map`` argument, which gives the significance of a feature (such as
+edges) being present at each pixel. In a region boundary RAG, the edge weight
+between two regions is the average value of the corresponding pixels in
+``edge_map`` along their shared boundary.
+
 """
 from skimage.future import graph
 from skimage import data, segmentation, color, filters, io