"""
https://en.wikipedia.org/wiki/Self-organizing_map
"""
import math
class SelfOrganizingMap:
def get_winner(self, weights: list[list[float]], sample: list[int]) -> int:
"""
Compute the winning vector by Euclidean distance
>>> SelfOrganizingMap().get_winner([[1, 2, 3], [4, 5, 6]], [1, 2, 3])
1
"""
d0 = 0.0
d1 = 0.0
for i in range(len(sample)):
d0 += math.pow((sample[i] - weights[0][i]), 2)
d1 += math.pow((sample[i] - weights[1][i]), 2)
return 0 if d0 > d1 else 1
return 0
def update(
self, weights: list[list[int | float]], sample: list[int], j: int, alpha: float
) -> list[list[int | float]]:
"""
Update the winning vector.
>>> SelfOrganizingMap().update([[1, 2, 3], [4, 5, 6]], [1, 2, 3], 1, 0.1)
[[1, 2, 3], [3.7, 4.7, 6]]
"""
for i in range(len(weights)):
weights[j][i] += alpha * (sample[i] - weights[j][i])
return weights
def main() -> None:
training_samples = [[1, 1, 0, 0], [0, 0, 0, 1], [1, 0, 0, 0], [0, 0, 1, 1]]
weights = [[0.2, 0.6, 0.5, 0.9], [0.8, 0.4, 0.7, 0.3]]
self_organizing_map = SelfOrganizingMap()
epochs = 3
alpha = 0.5
for _ in range(epochs):
for j in range(len(training_samples)):
sample = training_samples[j]
winner = self_organizing_map.get_winner(weights, sample)
weights = self_organizing_map.update(weights, sample, winner, alpha)
sample = [0, 0, 0, 1]
winner = self_organizing_map.get_winner(weights, sample)
print(f"Clusters that the test sample belongs to : {winner}")
print(f"Weights that have been trained : {weights}")
if __name__ == "__main__":
main()