NEARNEGH.SML

#************************************************************************
#The following code updates the two (previously defined)
#nearest neighbor databases:

# NEARNEGH.SML
# AUTHOR:  Paul Pope, Environmental Monitoring Program, UW-Madison
# LAST MODIFIED:  April 12, 1997
#
# This SML script updates the nearest
# neighbor databases for the polygons of a vector object.
# The following database tables must be defined before
# running the script:
#
# Table Name:  Num_NN
# Description:  The number of nearest neighbors for each polygon
# Number of Fields:  1
# Field: Number_Neighbors
# Field Type:  Integer (Width: 10, SLong)
# Attachment Type:  One Record Per Element
#
# Table Name:  NN
# Description:  The polygon number of the nearest neighbors for each polygon
# Number of Fields:  1
# Field Type:  Integer (Width: 10, SLong)
# Attachment Type:  No Restrictions
#

clear();

# Prompt the user to enter a vector object
vector V;
GetInputVector(V);

numeric number_of_polygons = NumVectorPolys(V);

# Loop over all the polygons in the vector object
numeric polygon_number;
for polygon_number = 1 to number_of_polygons step 1
{
	#   print(" ")
	#   print("Working on polgon number = ", polygon_number)

	array numeric line_list[1];
	array numeric nearest_neighbor_list[1];

	numeric number_of_lines = GetVectorPolyLineList(V, line_list, polygon_number);
	#  print("Number of Lines = ", number_of_lines)

	# Loop over all the lines which make up the current polygon
	numeric k;
	numeric number_of_neighbors = 0;
	numeric leftpoly, rightpoly, outside_polygon;
	numeric line_number, flag;
	for line_number = 1 to number_of_lines step 1
	{
		#     print("Line Number = ", line_list[line_number])

		leftpoly = V.line[line_list[line_number]].Internal.LeftPoly;
		rightpoly = V.line[line_list[line_number]].Internal.RightPoly;

		#     print("Left Poly = ", leftpoly, "Right Poly = ", rightpoly)

		# The polygon which is not the current polygon
		# is a neighbor polygon
		if (leftpoly != polygon_number) then
		{
			outside_polygon = leftpoly;
		}
		if (rightpoly != polygon_number) then
		{
			outside_polygon = rightpoly;
		}

		#     print("Outside polygon = ", outside_polygon)

		# Ensure that the neighbor polygon is not already
		# in the nearest neighbor list
		flag = 0;
		for k = 1 to number_of_neighbors step 1
		{
			if (nearest_neighbor_list[k] == outside_polygon) then
			{
				flag = 1;
			}
		}

		# If the neighbor polygon is not already in
		# the nearest neighbor list, add it to the list
		if (flag != 1) then
		{

		  # Make a copy of the nearest neighbor list
		  if (number_of_neighbors > 0) then
		  {
			array numeric temp_list[number_of_neighbors];
			for k = 1 to number_of_neighbors step 1
			{
				temp_list[k] = nearest_neighbor_list[k];
			}
		  }

		  # Enlarge the nearest neighbor list to include
		  # another entry and add the nearest neighbor to
		  # the end of the list
		  number_of_neighbors = number_of_neighbors + 1;
		  array numeric nearest_neighbor_list[number_of_neighbors];
		  nearest_neighbor_list[number_of_neighbors] = outside_polygon;

			# Copy the previous nearest neighbors to the
			# newly expanded list
			if (number_of_neighbors > 1) then
			{
				for k = 1 to (number_of_neighbors - 1) step 1
				{
					nearest_neighbor_list[k] = temp_list[k];
				}
			}

	#        print("Nearest Neighbor = ", outside_polygon)

		}  # End of flag if statement

	}  # End of looping over the number of lines

	# Update the nearest neighbor polygon database tables
	#   print("For polygon number = ", polygon_number,", ")
	#   print("the number of nearest neighbors = ", number_of_neighbors)
	V.poly[polygon_number].Num_NN.Number_NN = number_of_neighbors;
	for k = 1 to number_of_neighbors step 1
	{
	#     print("Nearest Neighbor[",k,"] = ", nearest_neighbor_list[k])
		V.poly[polygon_number].NN[k].NearestNeighbor = nearest_neighbor_list[k];
	}

}  # End of looping over the number of polygons

# End of SML script