Lloyd’s algorithm

E426673

Lloyd’s algorithm is an iterative clustering method that partitions data into k groups by repeatedly assigning points to the nearest cluster center and updating those centers to minimize within-cluster variance.

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Predicate Object
instanceOf clustering algorithm
iterative optimization method
unsupervised learning method
alsoKnownAs Lloyd–Forgy algorithm NERFINISHED
standard k-means algorithm NERFINISHED
assignmentStepDescription assign each point to the nearest cluster center
assumes Euclidean distance metric by default
canUse other distance metrics with modifications
category k-means methods
commonInitializationMethod Forgy method NERFINISHED
k-means++ initialization
random selection of initial centers
convergesWhen change in objective function is below a threshold
cluster assignments no longer change
doesNotGuarantee global optimum
field information theory
machine learning
statistics
firstPublishedIn 1982
guarantees convergence to a local minimum of the objective function
hasStep assignment step
convergence check
initialization of k cluster centers
update step
input number of clusters k
set of data points
limitation may converge to poor local minima
requires pre-specifying number of clusters k
sensitive to outliers and noise
minimizes sum of squared distances to cluster centers
within-cluster variance
objectiveFunction within-cluster sum of squares
optimizationType local optimization
originalApplicationDomain pulse-code modulation
output cluster assignments for each data point
k cluster centers
proposedBy Stuart P. Lloyd NERFINISHED
proposedIn 1957
relatedTo Forgy algorithm
expectation–maximization algorithm
k-means++ NERFINISHED
sensitiveTo initialization of cluster centers
timeComplexity O(n k d i)
timeComplexityDescription n data points, k clusters, d dimensions, i iterations
typicalUseCase clustering in data mining
image compression
signal quantization
updateStepDescription recompute each cluster center as the mean of its assigned points
usedFor k-means clustering
partitioning data into k clusters
vector quantization

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KMeans alsoKnownAs Lloyd’s algorithm