calculate link matrix

lib/rock/links.ex

@@ -0,0 +1,67 @@
+defmodule Rock.Links do
+  alias Rock.JaccardCoefficient
+  alias Rock.Neighbours
+
+  def matrix(points, theta, similarity_function \\ &JaccardCoefficient.measure/2)
+      when is_number(theta)
+      when is_list(points)do
+    neighbour_lists =
+      points
+      |> Neighbours.list(theta, similarity_function)
+
+    points
+    |> Enum.count
+    |> initialize_links
+    |> outer_loop(neighbour_lists)
+  end
+
+  def initialize_links(size) do
+    1..size
+    |> Enum.map(fn(_) ->
+      1..size
+      |> Enum.map(fn(_) ->
+        0
+      end)
+    end)
+  end
+
+  def outer_loop(link_matrix, [neighbour_list | []]) do
+    link_matrix
+    |> links_from_neighbours(neighbour_list)
+  end
+
+  def outer_loop(link_matrix, [neighbour_list | tail]) do
+    link_matrix
+    |> links_from_neighbours(neighbour_list)
+    |> outer_loop(tail)
+  end
+
+  def links_from_neighbours(link_matrix, [_neighbour | []]) do
+    link_matrix
+  end
+
+  def links_from_neighbours(link_matrix, [neighbour | neighbour_tail]) do
+    link_matrix
+    |> add_links(neighbour_tail, neighbour)
+    |> links_from_neighbours(neighbour_tail)
+  end
+
+  def add_links(link_matrix, [neighbour | []], row_index) do
+    link_matrix
+    |> add_link(row_index, neighbour)
+  end
+
+  def add_links(link_matrix, [neighbour | neighbour_tail], row_index) do
+    link_matrix
+    |> add_link(row_index, neighbour)
+    |> add_links(neighbour_tail, row_index)
+  end
+
+  def add_link(link_matrix, row_index, column_index) do
+    link_matrix
+    |> List.update_at(row_index, fn(row) ->
+      row
+      |> List.update_at(column_index,  &(&1 + 1))
+    end)
+  end
+end

lib/rock/neighbours.ex

@@ -1,19 +1,11 @@
 defmodule Rock.Neighbours do
-  alias Rock.JaccardCoefficient
-
-  def list(points,
-      theta,
-      similarity_function \\ &JaccardCoefficient.measure/2)
-      when is_list(points) do
+  def list(points, theta, similarity_function) when is_list(points) do
     points
     |> matrix(theta, similarity_function)
     |> index_list
   end
 
-  def matrix(points,
-      theta,
-      similarity_function \\ &JaccardCoefficient.measure/2)
-      when is_list(points) do
+  def matrix(points, theta, similarity_function) when is_list(points) do
     similarity_function = fn(point1, point2) ->
       neighbors?(point1, point2, similarity_function, theta)
     end

test/rock/links_test.exs

@@ -0,0 +1,24 @@
+defmodule Rock.LinksTest do
+  use ExUnit.Case
+  alias Rock.Links
+  alias Rock.Struct.Point
+
+  @points [
+    Point.new(["1", "2", "3", "4", "5"]),
+    Point.new(["1"]),
+    Point.new(["5", "6", "7"])
+  ]
+
+  test "calculates link matrix" do
+    link_matrix =
+      @points
+      |> Links.matrix(0)
+
+    ^link_matrix =
+      [
+        [0, 2, 2],
+        [0, 0, 1],
+        [0, 0, 0]
+      ]
+  end
+end

test/rock/neighbours_test.exs

@@ -2,6 +2,7 @@ defmodule Rock.NeighboursTest do
   use ExUnit.Case
   alias Rock.Struct.Point
   alias Rock.Neighbours
+  alias Rock.JaccardCoefficient
 
   @points [
     Point.new(["1", "2", "3", "4", "5"]),
@@ -10,7 +11,9 @@ defmodule Rock.NeighboursTest do
   ]
 
   test "calculates neighbor matrix with jaccard coefficient" do
-    neighbor_matrix = @points |> Neighbours.matrix(0.1)
+    neighbor_matrix =
+      @points
+      |> Neighbours.matrix(0.1, &JaccardCoefficient.measure/2)
 
     ^neighbor_matrix = [
       [1, 1, 1],
@@ -37,7 +40,9 @@ defmodule Rock.NeighboursTest do
   end
 
   test "returns neighbor indices list" do
-    neighbor_list = @points |> Neighbours.list(0.1)
+    neighbor_list =
+      @points
+      |> Neighbours.list(0.1, &JaccardCoefficient.measure/2)
 
     ^neighbor_list = [
       [0, 1, 2],