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Algorithmic Thinking in Bioinformatics · End Term · 13 Apr 2025 · January 2025 term

Question 3: In a soft K-means clustering process, a dataset is cluste…

Question 3

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In a soft K-means clustering process, a dataset is clustered into two groups. A data point has distances d1=3d_1 = 3 and d2=6d_2 = 6 from the two cluster centroids. Using the soft K-means formula with β=1\beta = 1, compute the probabilities of the data point belonging to each cluster.

After assigning probabilities, update the centroid μ1\mu_1 given that the current centroid is μ1=4\mu_1 = 4 and this data point's value is x=5x = 5. Assume no other points are assigned to cluster 1. Use the centroid update formula:

μknew=∑iP(Ck∣xi)xi∑iP(Ck∣xi)\mu_k^{\text{new}} = \frac{\sum_i P(C_k \mid x_i) x_i}{\sum_i P(C_k \mid x_i)}

where P(Ck∣x)P(C_k \mid x) is computed using the softmax-like probability formula:

P(Ck∣x)=e−βdk∑j=1Ke−βdjP(C_k \mid x) = \frac{e^{-\beta d_k}}{\sum_{j=1}^{K} e^{-\beta d_j}}

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Question 3 of 19 in the IIT Madras BS Algorithmic Thinking in Bioinformatics (Algorithmic Thinking in Bioinformatics) End Term paper sat on 13 Apr 2025, in the January 2025 term (IIT M IMPROVEMENT AN EXAM QIM3 13 Apr 2025). It carries 4 marks.

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