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K-Means Clustering Algorithm
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K-Means Clustering Algorithm

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Questions and Answers

What is one natural application of classification techniques in finance?

  • Anomaly detection
  • Feature selection
  • Sentiment analysis (correct)
  • Data compression
  • Which method is a tool used for data visualization or data pre-processing before supervised techniques are applied?

  • KNN
  • Self organizing maps
  • Principal components analysis (correct)
  • Clustering
  • What is a broad class of methods for discovering unknown subgroups in data?

  • Feature selection
  • Data compression
  • Anomaly detection
  • Clustering (correct)
  • Which type of learning does not require labeling of the data?

    <p>Unsupervised learning</p> Signup and view all the answers

    What is an example of a potential application where unsupervised learning is helpful?

    <p>Earnings reports analysis</p> Signup and view all the answers

    Which technique is mentioned specifically for timing of risk premia strategies?

    <p>Time series analysis</p> Signup and view all the answers

    What controls the number of clusters in hierarchical clustering?

    <p>The height of the cut</p> Signup and view all the answers

    What is the main difference between average and complete linkage in hierarchical clustering?

    <p>Their tendency to generate balanced dendrograms</p> Signup and view all the answers

    Why is the choice of dissimilarity measure crucial in hierarchical clustering?

    <p>It affects the interpretability of the dendrogram</p> Signup and view all the answers

    What is the key consideration for drawing conclusions on similarity in hierarchical clustering?

    <p>Making a horizontal cut across the dendrogram</p> Signup and view all the answers

    Which dissimilarity measures are commonly used in hierarchical clustering?

    <p>$Euclidean$ distance and correlation-based distance</p> Signup and view all the answers

    What is the primary advantage of K Means clustering over hierarchical clustering?

    <p>Linear time complexity</p> Signup and view all the answers

    How do observations fuse together in hierarchical clustering?

    <p>From bottom to top, creating nested clusters</p> Signup and view all the answers

    Why is it important to visually determine the optimal number of clusters in hierarchical clustering?

    <p>To find an interpretable pattern in the data</p> Signup and view all the answers

    What is a key difference between K Means and hierarchical clustering?

    <p>K Means requires prior knowledge of number of clusters, while hierarchical clustering allows interpretation of dendrogram for cluster determination.</p> Signup and view all the answers

    What does principal component analysis (PCA) aim to capture in high-dimensional datasets?

    <p>Most of the variance</p> Signup and view all the answers

    What function is commonly used to measure within-cluster variation in K-means clustering?

    <p>Euclidean norm</p> Signup and view all the answers

    In K-means clustering, what does 'closeness' between observations refer to?

    <p>Distance from each other</p> Signup and view all the answers

    What type of learning problem is clustering considered?

    <p>Unsupervised learning</p> Signup and view all the answers

    What characteristic makes it challenging to imagine high-dimensional spaces?

    <p>The curse of dimensionality</p> Signup and view all the answers

    What is the primary goal of K-means clustering?

    <p>Partition data into mutually exclusive clusters based on distance from each point to cluster's center</p> Signup and view all the answers

    What does hierarchical clustering visualize data using?

    <p>A tree structure</p> Signup and view all the answers

    In K-Means clustering, why is it important to run the algorithm several times starting from various initial random clusters?

    <p>To find the most stable clusters and mitigate the sensitivity to the initial choice of cluster centers.</p> Signup and view all the answers

    What is a key advantage of hierarchical clustering over K-Means clustering?

    <p>It does not require choosing the number of clusters and creates a dendrogram representation.</p> Signup and view all the answers

    What does a scree plot help determine in K-Means clustering?

    <p>The optimal number of clusters based on the error decreasing function.</p> Signup and view all the answers

    Why is standardizing features before computing distance almost always recommended in K-Means clustering?

    <p>To prevent features with larger scales from dominating the distance calculations.</p> Signup and view all the answers

    What is agglomerative hierarchical clustering?

    <p>A type where clusters are formed by merging closest points until all points are in a single cluster.</p> Signup and view all the answers

    What is one common application of K-Means clustering mentioned in the text?

    <p>Customer segmentation in marketing analysis.</p> Signup and view all the answers

    What is the primary goal of principal components analysis (PCA) in unsupervised learning?

    <p>To visualize high-dimensional data</p> Signup and view all the answers

    Which technique is specifically mentioned for timing of risk premia strategies in unsupervised learning?

    <p>KNN</p> Signup and view all the answers

    What is a characteristic of unsupervised learning mentioned in the text?

    <p>It is more subjective with no simple goal for the analysis</p> Signup and view all the answers

    What is a common application of classification techniques in finance mentioned in the text?

    <p>Credit Rating</p> Signup and view all the answers

    What type of learning does not require labeling of the data, as mentioned in the text?

    <p>Unsupervised learning</p> Signup and view all the answers

    What is a key advantage of hierarchical clustering over K-Means clustering, as mentioned in the text?

    <p>It visualizes data using a tree structure</p> Signup and view all the answers

    What is a broad class of methods for discovering unknown subgroups in data, as mentioned in the text?

    <p>Clustering</p> Signup and view all the answers

    What is the total number of possible representations of the tree in hierarchical clustering, considering fusion points and multiple ways of representing the fusing leaves?

    <p>$2n-1$</p> Signup and view all the answers

    In hierarchical clustering, how do observations fuse together to create nested clusters?

    <p>From bottom to top</p> Signup and view all the answers

    What controls the number of clusters in hierarchical clustering?

    <p>The height of the cut</p> Signup and view all the answers

    Which dissimilarity measures are commonly used in hierarchical clustering?

    <p>Euclidean distance and correlation-based distance</p> Signup and view all the answers

    What is a key consideration for drawing conclusions on similarity in hierarchical clustering?

    <p>Taking a horizontal cut of the dendrogram</p> Signup and view all the answers

    What is the primary advantage of K Means clustering over hierarchical clustering?

    <p>Linear time complexity</p> Signup and view all the answers

    What does hierarchical clustering visualize data using?

    <p>Dendrogram</p> Signup and view all the answers

    Which type of learning does not require labeling of the data?

    <p>Unsupervised learning</p> Signup and view all the answers

    What is one common application of K-Means clustering mentioned in the text?

    <p>Customer segmentation in marketing</p> Signup and view all the answers

    What is the primary goal of principal component analysis (PCA) in high-dimensional datasets?

    <p>Capturing most of the variance in the data</p> Signup and view all the answers

    What measure of distance is commonly used to define 'closeness' between observations in K-means clustering?

    <p>Euclidean norm</p> Signup and view all the answers

    In which type of clustering does data get visualized using a tree structure?

    <p>Hierarchical clustering</p> Signup and view all the answers

    Why is K-means clustering suitable for fast clustering of large datasets?

    <p>It minimizes within-cluster variation collectively to find the clusters</p> Signup and view all the answers

    What does the curse of dimensionality make it hard to imagine?

    <p>$200$-dimensional ellipsoid in a $1,000$-dimensional space</p> Signup and view all the answers

    What is one key characteristic of K-means clustering?

    <p>It requires guessing the centers and iterating until convergence</p> Signup and view all the answers

    Which type of learning problem does K-means clustering exemplify?

    <p>Unsupervised learning problem</p> Signup and view all the answers

    What is a potential drawback of K-Means clustering?

    <p>Sensitive to initial choice of cluster centers</p> Signup and view all the answers

    What is a key advantage of hierarchical clustering over K-Means clustering?

    <p>Does not require choosing the number of clusters</p> Signup and view all the answers

    What is the primary goal of running K-Means algorithm on various subsets of training data?

    <p>Understand stability of clusters</p> Signup and view all the answers

    Why is standardizing features before computing distance almost always recommended in K-Means clustering?

    <p>To ensure features have equal influence on the clustering process</p> Signup and view all the answers

    What does a scree plot help determine in K-Means clustering?

    <p>Optimal number of clusters based on error decreasing function</p> Signup and view all the answers

    What is a key consideration for drawing conclusions on similarity in hierarchical clustering?

    <p>'Linkage' method used for merging clusters</p> Signup and view all the answers

    What characteristic makes hierarchical clustering an effective approach for high-dimensional data?

    <p>Ability to capture complex relationships between features</p> Signup and view all the answers

    Study Notes

    Understanding K-Means Clustering and Hierarchical Clustering

    • K-Means algorithm involves scaling the data, selecting initial cluster centers, measuring distances of data points to the centers, finding the centroids, and repeating until convergence.
    • A scree plot can be used to determine the optimal number of clusters in K-Means clustering, based on the error decreasing function of the number of clusters.
    • K-Means clustering can be applied to financial data, such as calculating volatility clusters based on historical time series, and can be used to compute a matrix of probabilities for transitioning between clusters.
    • To ensure the best results in K-Means clustering, the algorithm should be run several times starting from various initial random clusters, and results should be compared to find the most stable clusters.
    • Selecting the number of clusters K in K-Means clustering is crucial, and it requires experimentation and analyzing the results for different values of K.
    • Standardizing features before computing the distance is almost always a good idea in K-Means clustering to ensure accurate results.
    • Hierarchical clustering is an alternative to K-Means clustering that does not require choosing the number of clusters and creates a dendrogram representation.
    • Agglomerative hierarchical clustering is the most common type, where each observation represents a leaf in a tree-like structure, and clusters are formed by merging closest points until all points are in a single cluster.
    • Dendrograms in hierarchical clustering show different possible clusterings, from a single cluster to n clusters, and the process starts with each point in its own cluster and merges the closest clusters until all points are in a single cluster.
    • Understanding agglomerative dendrograms involves starting from the leaves and moving up to comprehend how clusters are formed.
    • K-Means clustering is sensitive to the initial choice of cluster centers, and running the algorithm on various subsets of training data can help understand the stability of clusters and if the right number of clusters has been chosen.
    • K-Means clustering can be used in various scenarios, such as grouping people based on different attributes like gender and mother tongue, and experimenting with different subsets of training data to determine stable clusters.

    Understanding K-Means Clustering and Hierarchical Clustering

    • K-Means algorithm involves scaling the data, selecting initial cluster centers, measuring distances of data points to the centers, finding the centroids, and repeating until convergence.
    • A scree plot can be used to determine the optimal number of clusters in K-Means clustering, based on the error decreasing function of the number of clusters.
    • K-Means clustering can be applied to financial data, such as calculating volatility clusters based on historical time series, and can be used to compute a matrix of probabilities for transitioning between clusters.
    • To ensure the best results in K-Means clustering, the algorithm should be run several times starting from various initial random clusters, and results should be compared to find the most stable clusters.
    • Selecting the number of clusters K in K-Means clustering is crucial, and it requires experimentation and analyzing the results for different values of K.
    • Standardizing features before computing the distance is almost always a good idea in K-Means clustering to ensure accurate results.
    • Hierarchical clustering is an alternative to K-Means clustering that does not require choosing the number of clusters and creates a dendrogram representation.
    • Agglomerative hierarchical clustering is the most common type, where each observation represents a leaf in a tree-like structure, and clusters are formed by merging closest points until all points are in a single cluster.
    • Dendrograms in hierarchical clustering show different possible clusterings, from a single cluster to n clusters, and the process starts with each point in its own cluster and merges the closest clusters until all points are in a single cluster.
    • Understanding agglomerative dendrograms involves starting from the leaves and moving up to comprehend how clusters are formed.
    • K-Means clustering is sensitive to the initial choice of cluster centers, and running the algorithm on various subsets of training data can help understand the stability of clusters and if the right number of clusters has been chosen.
    • K-Means clustering can be used in various scenarios, such as grouping people based on different attributes like gender and mother tongue, and experimenting with different subsets of training data to determine stable clusters.

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    lecture 07.pdf

    Description

    Learn about the K-means clustering algorithm and its steps, including scaling the data, selecting initial centers, and measuring distances to assign data points to clusters.

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