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mdwtcluster

Multisignals 1-D clustering

    Description

    s = mdwtcluster(x) clusters data using hierarchical clustering. The input matrix x is decomposed in the row direction using the discrete wavelet transform (DWT) with the Haar wavelet and the maximum allowed level fix(log2(size(x,2))).

    Note

    mdwtcluster requires Statistics and Machine Learning Toolbox™.

    example

    s = mdwtcluster(___,Name,Value) specifies options using name-value pair arguments in addition to the input argument in the previous syntax. For example, 'level',4 specifies the decomposition level.

    Examples

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    Load the 1-D multisignal elecsig10.

    load elecsig10

    Compute the structure resulting from multisignal clustering.

    lst2clu = {'s','ca1','ca3','ca6'};
    S = mdwtcluster(signals,'maxclust',4,'lst2clu',lst2clu)
    S = struct with fields:
        IdxCLU: [70x4 double]
        Incons: [69x4 double]
          Corr: [0.7920 0.7926 0.7947 0.7631]
    
    

    Retrieve the cluster indices.

    IdxCLU = S.IdxCLU;

    Plot the first and third clusters.

    plot(signals(IdxCLU(:,1)==1,:)','r')
    hold on
    plot(signals(IdxCLU(:,1)==3,:)','b')
    hold off
    title('Cluster 1 (Signal) and Cluster 3 (Coefficients)')

    Check the equality of partitions. Confirm we obtain the same partitions using coefficients of approximation at level 3 instead of the original signals. Much less information is then used.

    equalPART = isequal(IdxCLU(:,1),IdxCLU(:,3))
    equalPART = logical
       1
    
    

    Input Arguments

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    Input data, specified as a matrix.

    Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

    Name-Value Pair Arguments

    Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

    Example: s = mdwtcluster(signals,'maxclust',4,'wname','db4') specifies four clusters and the wavelet db4.

    Direction of decomposition, specified as 'r' (row) or 'c' (column).

    Level of DWT decomposition, specified as a positive integer. The default value is fix(log2(size(x,d))), where d=1 or d=2, depending on the dirDec value.

    Wavelet used for the DWT, specified as a character vector or string scalar. The default value is the Haar wavelet, 'haar'.

    DWT extension mode, specified as a character vector or string scalar. See dwtmode.

    Distance metric, specified as a character vector, string scalar, or function handle. The default value is 'euclidean'. See pdist (Statistics and Machine Learning Toolbox).

    Algorithm for computing the distance between clusters, specified as one of the values in this table.

    MethodDescription
    'average'

    Unweighted average distance (UPGMA)

    'centroid'

    Centroid distance (UPGMC), appropriate for Euclidean distances only

    'complete'

    Farthest distance

    'median'

    Weighted center of mass distance (WPGMC), appropriate for Euclidean distances only

    'single'

    Shortest distance

    'ward'

    Inner squared distance (minimum variance algorithm), appropriate for Euclidean distances only

    'weighted'

    Weighted average distance (WPGMA)

    See linkage (Statistics and Machine Learning Toolbox).

    Number of clusters, specified as an integer or vector.

    Cell array of character vectors or string vector which contains the list of data to classify. If N is the level of decomposition, the allowed name values for the cells are:

    • 's' — Signal

    • 'aj' — Approximation at level j

    • 'dj' — Detail at level j

    • 'caj' — Coefficients of approximation at level j

    • 'cdj' — Coefficients of detail at level j

    with j = 1, …, N.

    The default value is {'s';'ca1';...;'caN'} or ["s" "cal" ... "caN"].

    Output Arguments

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    The output structure s is such that for each partition j:

    S.Idx(:,j)

    Contains the cluster numbers obtained from the hierarchical cluster tree. See cluster (Statistics and Machine Learning Toolbox).

    S.Incons(:,j)

    Contains the inconsistent values of each non-leaf node in the hierarchical cluster tree. See inconsistent (Statistics and Machine Learning Toolbox).

    S.Corr(j)

    Contains the cophenetic correlation coefficients of the partition. See cophenet (Statistics and Machine Learning Toolbox).

    Note

    If maxclust is a vector, then IdxCLU is a multidimensional array such that IdxCLU(:,j,k) contains the cluster numbers obtained from the hierarchical cluster tree for k clusters.

    See Also

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    Introduced in R2008a