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method predict

Pelajaran 11 dari 19 dalam kursus Pengantar Machine Learning di Coddy.

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method predict menghitung jarak setiap titik baru ke semua centroid lainnya. Titik tersebut dimasukkan ke cluster dengan centroid terdekat. 

Untuk setiap titik baru, tetapkan indeks centroid terdekat. Kembalikan list cluster yang diprediksi.

Coba sendiri

def euclidian_distance(point_a, point_b):
    return (sum([(point_a[i] - point_b[i])**2 for i in range(len(point_a))]))**0.5

class KMeans:
    def __init__(self, k):
        self.k = k

    def find_cluster_centroid(self, cluster_points):
    # Write your code here
        centroid = []
        for point in cluster_points:
            for dim, value in enumerate(point):
                if len(centroid) - 1 < dim:
                    centroid.append(0)
                centroid[dim] += value
        for i in range(len(centroid)):
            centroid[i] /= len(cluster_points)
        return centroid

    def fit(self, X_train):
        # Write you code here
        self.centroids = [X_train[i] for i in range(2, self.k*2 + 1, 2)]
        while True:
            # Assing each point to centroid
            points_clusters = []
            for point in X_train:
                distances = []
                for centroid in self.centroids:
                    dist_to_point = euclidian_distance(centroid, point)
                    distances.append(dist_to_point)
                closest_centroid_index = distances.index(min(distances))
                points_clusters.append((point, closest_centroid_index))

            # Update centroids
            clusters = {}
            for point, cluster in points_clusters:
                if cluster not in clusters:
                    clusters[cluster] = []
                clusters[cluster].append(point)
            new_centroids = [None]*self.k
            for cluster, points in clusters.items():
                new_centroids[cluster] = self.find_cluster_centroid(points)

            # Check if converged
            total_dist = 0
            for i in range(len(new_centroids)):
                total_dist += euclidian_distance(new_centroids[i], self.centroids[i])
            if total_dist < 0.01:
                break
            self.centroids = new_centroids


    def predict(self, X_test):
        pass

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Latihan sendiri: Compiler Python online