kmeans example in cpp and python (#356)

Signed-off-by: Alejandro Hernández <[email protected]>

examples/CMakeLists.txt

@@ -31,5 +31,8 @@ target_link_libraries(rand_example ignition-math${IGN_MATH_VER}::ignition-math${
 add_executable(graph_example graph_example.cc)
 target_link_libraries(graph_example ignition-math${IGN_MATH_VER}::ignition-math${IGN_MATH_VER})
 
+add_executable(kmeans kmeans.cc)
+target_link_libraries(kmeans ignition-math${IGN_MATH_VER}::ignition-math${IGN_MATH_VER})
+
 add_executable(color_example color_example.cc)
 target_link_libraries(color_example ignition-math${IGN_MATH_VER}::ignition-math${IGN_MATH_VER})

examples/kmeans.cc

@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2021 Open Source Robotics Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+*/
+
+#include <iostream>
+#include <vector>
+
+#include <ignition/math/Kmeans.hh>
+
+int main(int argc, char **argv)
+{
+  // Create some observations.
+  std::vector<ignition::math::Vector3d> obs;
+  obs.push_back(ignition::math::Vector3d(1.0, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(1.1, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(1.2, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(1.3, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(1.4, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(5.0, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(5.1, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(5.2, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(5.3, 1.0, 0.0));
+  obs.push_back(ignition::math::Vector3d(5.4, 1.0, 0.0));
+
+  // Initialize Kmeans with two partitions.
+  ignition::math::Kmeans kmeans(obs);
+
+  std::vector<ignition::math::Vector3d> obsCopy;
+  obsCopy = kmeans.Observations();
+
+  for (auto &elem : obsCopy)
+    elem += ignition::math::Vector3d(0.1, 0.2, 0.0);
+
+  // append more observations
+  kmeans.AppendObservations(obsCopy);
+
+  // cluster
+  std::vector<ignition::math::Vector3d> centroids;
+  std::vector<unsigned int> labels;
+  auto result = kmeans.Cluster(2, centroids, labels);
+
+  // Check that there are two centroids.
+  std::cout << "Is there a solution ? " << result << std::endl;
+  std::cout << "There are " << centroids.size() << " centroids" << std::endl;
+  std::cout << "labels: [";
+  for (auto &label: labels)
+  {
+    std::cout << label << ", ";
+  }
+  std::cout << "]" << '\n';
+}

examples/kmeans.py

@@ -0,0 +1,51 @@
+# Copyright (C) 2021 Open Source Robotics Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License")
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from ignition.math import Kmeans, Vector3d
+
+# Create some observations.
+obs = list([])
+obs.append(Vector3d(1.0, 1.0, 0.0))
+obs.append(Vector3d(1.1, 1.0, 0.0))
+obs.append(Vector3d(1.2, 1.0, 0.0))
+obs.append(Vector3d(1.3, 1.0, 0.0))
+obs.append(Vector3d(1.4, 1.0, 0.0))
+obs.append(Vector3d(5.0, 1.0, 0.0))
+obs.append(Vector3d(5.1, 1.0, 0.0))
+obs.append(Vector3d(5.2, 1.0, 0.0))
+obs.append(Vector3d(5.3, 1.0, 0.0))
+obs.append(Vector3d(5.4, 1.0, 0.0))
+
+# Initialize Kmeans with two partitions.
+kmeans = Kmeans(obs)
+
+# copy original Vector to add more data
+obs_copy = list(kmeans.observations()).copy()
+obs2 = list([])
+
+for idx, a in enumerate(obs_copy):
+    obs_copy[idx] = a + Vector3d(0.1, 0.2, 0.0)
+    obs2.append(obs_copy[idx])
+
+# Append more observations
+kmeans.append_observations(obs2)
+
+# Calling cluster
+result, centroids, labels = kmeans.cluster(2)
+
+# Check that there are two centroids.
+print("Is there a solution ? {}".format(result));
+print("There are {} centroids".format(len(centroids)))
+print("labels:", labels)