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 examples demonstrates how to perform hierarchical merging on region
+boundary Region Adjacency Grapghs (RAGs). Region boundary RAGs can be
+contructed 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 contruct region boundary based RAGs, see
+:any:`plot_rag_boundary`
+
 """
 
 from skimage import data, segmentation, filters, color

doc/examples/segmentation/plot_rag_boundary.py

@@ -4,7 +4,12 @@ Region Boundary based RAGs
 ==========================
 
 This example demonstrates construction of region boundary based RAGs with the
-`rag_boundary` function.
+:py:func:`skimage.future.graph.rag_boundary` function. The function taken 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 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