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"""! |
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@brief Cluster analysis algorithm: agglomerative algorithm. |
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@details Implementation based on book: |
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- K.Anil, J.C.Dubes, R.C.Dubes. Algorithms for Clustering Data. 1988. |
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@authors Andrei Novikov ([email protected]) |
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@date 2014-2017 |
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@copyright GNU Public License |
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@cond GNU_PUBLIC_LICENSE |
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PyClustering is free software: you can redistribute it and/or modify |
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it under the terms of the GNU General Public License as published by |
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the Free Software Foundation, either version 3 of the License, or |
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(at your option) any later version. |
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PyClustering is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU General Public License for more details. |
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You should have received a copy of the GNU General Public License |
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along with this program. If not, see <http://www.gnu.org/licenses/>. |
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@endcond |
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""" |
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from enum import IntEnum; |
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from pyclustering.cluster.encoder import type_encoding; |
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from pyclustering.utils import euclidean_distance_sqrt; |
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import pyclustering.core.agglomerative_wrapper as wrapper; |
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class type_link(IntEnum): |
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"""! |
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@brief Enumerator of types of link between clusters. |
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""" |
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## The nearest objects in clusters is considered as a link. |
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SINGLE_LINK = 0; |
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## The farthest objects in clusters is considered as a link. |
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COMPLETE_LINK = 1; |
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## Average distance between objects in clusters is considered as a link. |
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AVERAGE_LINK = 2; |
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## Distance between centers of clusters is considered as a link. |
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CENTROID_LINK = 3; |
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class agglomerative: |
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"""! |
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@brief Class represents agglomerative algorithm for cluster analysis. |
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@details Agglomerative algorithm considers each data point (object) as a separate cluster at the beggining and |
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step by step finds the best pair of clusters for merge until required amount of clusters is obtained. |
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Example of agglomerative algorithm where centroid link is used: |
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@code |
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# sample for cluster analysis (represented by list) |
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sample = read_sample(path_to_sample); |
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# create object that uses python code only |
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agglomerative_instance = agglomerative(sample, 2, link_type.CENTROID_LINK) |
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# cluster analysis |
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agglomerative_instance.process(); |
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# obtain results of clustering |
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clusters = agglomerative_instance.get_clusters(); |
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@endcode |
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Algorithm performance can be improved if 'ccore' flag is on. In this case C++ library will be called for clustering. |
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There is example of clustering 'LSUN' sample when usage of single or complete link will take a lot of resources and |
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when core usage is prefereble. |
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@code |
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# sample Lsun for cluster analysis |
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lsun_sample = read_sample(FCPS_SAMPLES.SAMPLE_LSUN); |
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# create instance of the algorithm that will use ccore library (the last argument) |
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agglomerative_instance = agglomerative(lsun_sample, 3, link_type.SINGLE_LINK, True); |
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# start processing |
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agglomerative_instance.process(); |
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# get result and visualize it |
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lsun_clusters = agglomerative_instance.get_clusters(); |
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visualizer = cluster_visualizer(); |
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visualizer.append_clusters(lsun_clusters, lsun_sample); |
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visualizer.show(); |
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@endcode |
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Example of agglomerative clustering using different links: |
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@image html agglomerative_lsun_clustering_single_link.png |
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""" |
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def __init__(self, data, number_clusters, link = None, ccore = False): |
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"""! |
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@brief Constructor of agglomerative hierarchical algorithm. |
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@param[in] data (list): Input data that is presented as a list of points (objects), each point should be represented by list, for example |
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[[0.1, 0.2], [0.4, 0.5], [1.3, 0.9]]. |
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@param[in] number_clusters (uint): Number of clusters that should be allocated. |
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@param[in] link (type_link): Link type that is used for calculation similarity between objects and clusters, if it is not specified centroid link will be used by default. |
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@param[in] ccore (bool): Defines should be CCORE (C++ pyclustering library) used instead of Python code or not (by default it is 'False'). |
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""" |
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self.__pointer_data = data; |
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self.__number_clusters = number_clusters; |
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self.__similarity = link; |
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if (self.__similarity is None): |
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self.__similarity = type_link.CENTROID_LINK; |
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self.__clusters = []; |
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self.__ccore = ccore; |
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if (self.__similarity == type_link.CENTROID_LINK): |
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self.__centers = self.__pointer_data.copy(); # used in case of usage of centroid links |
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def process(self): |
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"""! |
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@brief Performs cluster analysis in line with rules of agglomerative algorithm and similarity. |
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@see get_clusters() |
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""" |
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if (self.__ccore is True): |
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self.__clusters = wrapper.agglomerative_algorithm(self.__pointer_data, self.__number_clusters, self.__similarity); |
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else: |
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self.__clusters = [[index] for index in range(0, len(self.__pointer_data))]; |
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current_number_clusters = len(self.__clusters); |
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while (current_number_clusters > self.__number_clusters): |
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self.__merge_similar_clusters(); |
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current_number_clusters = len(self.__clusters); |
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def get_clusters(self): |
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"""! |
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@brief Returns list of allocated clusters, each cluster contains indexes of objects in list of data. |
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@remark Results of clustering can be obtained using corresponding gets methods. |
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@return (list) List of allocated clusters, each cluster contains indexes of objects in list of data. |
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@see process() |
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""" |
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return self.__clusters; |
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def get_cluster_encoding(self): |
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"""! |
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@brief Returns clustering result representation type that indicate how clusters are encoded. |
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@return (type_encoding) Clustering result representation. |
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@see get_clusters() |
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""" |
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return type_encoding.CLUSTER_INDEX_LIST_SEPARATION; |
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def __merge_similar_clusters(self): |
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"""! |
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@brief Merges the most similar clusters in line with link type. |
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""" |
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if (self.__similarity == type_link.AVERAGE_LINK): |
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self.__merge_by_average_link(); |
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elif (self.__similarity == type_link.CENTROID_LINK): |
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self.__merge_by_centroid_link(); |
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elif (self.__similarity == type_link.COMPLETE_LINK): |
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self.__merge_by_complete_link(); |
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elif (self.__similarity == type_link.SINGLE_LINK): |
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self.__merge_by_signle_link(); |
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else: |
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raise NameError('Not supported similarity is used'); |
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def __merge_by_average_link(self): |
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"""! |
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@brief Merges the most similar clusters in line with average link type. |
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""" |
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minimum_average_distance = float('Inf'); |
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View Code Duplication |
for index_cluster1 in range(0, len(self.__clusters)): |
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for index_cluster2 in range(index_cluster1 + 1, len(self.__clusters)): |
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# Find farthest objects |
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candidate_average_distance = 0.0; |
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for index_object1 in self.__clusters[index_cluster1]: |
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for index_object2 in self.__clusters[index_cluster2]: |
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candidate_average_distance += euclidean_distance_sqrt(self.__pointer_data[index_object1], self.__pointer_data[index_object2]); |
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candidate_average_distance /= (len(self.__clusters[index_cluster1]) + len(self.__clusters[index_cluster2])); |
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if (candidate_average_distance < minimum_average_distance): |
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minimum_average_distance = candidate_average_distance; |
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indexes = [index_cluster1, index_cluster2]; |
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self.__clusters[indexes[0]] += self.__clusters[indexes[1]]; |
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self.__clusters.pop(indexes[1]); # remove merged cluster. |
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def __merge_by_centroid_link(self): |
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"""! |
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@brief Merges the most similar clusters in line with centroid link type. |
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""" |
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minimum_centroid_distance = float('Inf'); |
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indexes = None; |
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for index1 in range(0, len(self.__centers)): |
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for index2 in range(index1 + 1, len(self.__centers)): |
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distance = euclidean_distance_sqrt(self.__centers[index1], self.__centers[index2]); |
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if (distance < minimum_centroid_distance): |
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minimum_centroid_distance = distance; |
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indexes = [index1, index2]; |
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self.__clusters[indexes[0]] += self.__clusters[indexes[1]]; |
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self.__centers[indexes[0]] = self.__calculate_center(self.__clusters[indexes[0]]); |
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self.__clusters.pop(indexes[1]); # remove merged cluster. |
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self.__centers.pop(indexes[1]); # remove merged center. |
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View Code Duplication |
def __merge_by_complete_link(self): |
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"""! |
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@brief Merges the most similar clusters in line with complete link type. |
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""" |
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minimum_complete_distance = float('Inf'); |
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indexes = None; |
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for index_cluster1 in range(0, len(self.__clusters)): |
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for index_cluster2 in range(index_cluster1 + 1, len(self.__clusters)): |
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candidate_maximum_distance = self.__calculate_farthest_distance(index_cluster1, index_cluster2); |
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if (candidate_maximum_distance < minimum_complete_distance): |
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minimum_complete_distance = candidate_maximum_distance; |
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indexes = [index_cluster1, index_cluster2]; |
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self.__clusters[indexes[0]] += self.__clusters[indexes[1]]; |
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self.__clusters.pop(indexes[1]); # remove merged cluster. |
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def __calculate_farthest_distance(self, index_cluster1, index_cluster2): |
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"""! |
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@brief Finds two farthest objects in two specified clusters in terms and returns distance between them. |
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@param[in] (uint) Index of the first cluster. |
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@param[in] (uint) Index of the second cluster. |
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@return The farthest euclidean distance between two clusters. |
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""" |
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candidate_maximum_distance = 0.0; |
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for index_object1 in self.__clusters[index_cluster1]: |
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for index_object2 in self.__clusters[index_cluster2]: |
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distance = euclidean_distance_sqrt(self.__pointer_data[index_object1], self.__pointer_data[index_object2]); |
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if (distance > candidate_maximum_distance): |
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candidate_maximum_distance = distance; |
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return candidate_maximum_distance; |
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def __merge_by_signle_link(self): |
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"""! |
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@brief Merges the most similar clusters in line with single link type. |
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""" |
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minimum_single_distance = float('Inf'); |
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indexes = None; |
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for index_cluster1 in range(0, len(self.__clusters)): |
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for index_cluster2 in range(index_cluster1 + 1, len(self.__clusters)): |
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candidate_minimum_distance = self.__calculate_nearest_distance(index_cluster1, index_cluster2); |
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if (candidate_minimum_distance < minimum_single_distance): |
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minimum_single_distance = candidate_minimum_distance; |
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indexes = [index_cluster1, index_cluster2]; |
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self.__clusters[indexes[0]] += self.__clusters[indexes[1]]; |
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self.__clusters.pop(indexes[1]); # remove merged cluster. |
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def __calculate_nearest_distance(self, index_cluster1, index_cluster2): |
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"""! |
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@brief Finds two nearest objects in two specified clusters and returns distance between them. |
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@param[in] (uint) Index of the first cluster. |
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@param[in] (uint) Index of the second cluster. |
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@return The nearest euclidean distance between two clusters. |
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""" |
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candidate_minimum_distance = float('Inf'); |
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for index_object1 in self.__clusters[index_cluster1]: |
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for index_object2 in self.__clusters[index_cluster2]: |
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distance = euclidean_distance_sqrt(self.__pointer_data[index_object1], self.__pointer_data[index_object2]); |
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if (distance < candidate_minimum_distance): |
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candidate_minimum_distance = distance; |
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return candidate_minimum_distance; |
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def __calculate_center(self, cluster): |
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"""! |
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@brief Calculates new center. |
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@return (list) New value of the center of the specified cluster. |
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""" |
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dimension = len(self.__pointer_data[cluster[0]]); |
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center = [0] * dimension; |
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for index_point in cluster: |
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for index_dimension in range(0, dimension): |
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center[index_dimension] += self.__pointer_data[index_point][index_dimension]; |
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for index_dimension in range(0, dimension): |
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center[index_dimension] /= len(cluster); |
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return center; |