quickselectFS

quickselectFS finds the k-th order statistic

Syntax

  • kE =quickselectFS(A,k)example
  • kE =quickselectFS(A,k,kiniindex)example
  • [kE , varargout]=quickselectFS(___)example

Description

example

kE =quickselectFS(A, k) quickselectFS with all default options.

example

kE =quickselectFS(A, k, kiniindex) quickselectFS with kiniindex supplied.

example

[kE , varargout] =quickselectFS(___) quickselectFS with two output arguments.

Examples

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  • quickselectFS with all default options.
  • n=200;
    Y=randn(n,1);
    k=10;
    [out]=quickselectFS(Y,k);
    % Check the result
    sorY=sort(Y);
    disp([out,sorY(k)])
       -1.5299   -1.5299
    
    

  • quickselectFS with kiniindex supplied.
  • n=200;
    Y=randn(n,1);
    k=10;
    % kiniindex is supplied 
    [out]=quickselectFS(Y,k,20);
    % Check the result
    sorY=sort(Y);
    disp([out,sorY(k)])
       -1.6085   -1.6085
    
    

  • quickselectFS with two output arguments.
  • n=10;
    Y=randn(n,1);
    k=3;
    % kiniindex is supplied 
    [out,Ysor]=quickselectFS(Y,k);
    % Check the result
    disp([Y, Ysor])
       -0.9290   -2.0480
       -1.8365   -1.8365
        2.0429   -1.1922
       -0.8267   -0.9290
       -0.8403   -0.8403
        1.9573   -0.8267
       -1.1922    0.4189
        0.4189    0.4323
       -2.0480    1.9573
        0.4323    2.0429
    
    

    Related Examples

    expand all

  • n=10;
    Y=1:n;
    Y = circshift(Y,-1);
    k=n;
    out=quickselectFS(Y,k);
    disp(out);

    Input Arguments

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    A — a set of unique numbers. Vector.

    Vector containing a set of n (distinct) numbers.

    Data Types: double

    k — order statistic index. Scalar.

    An integer between 1 and n indicating the desired order statistic.

    Data Types: double

    Optional Arguments

    kiniindex — Index of an element in A. Scalar.

    The index of an element in A that is supposed to be "close" to the desired k-th order statistic. This information is used to choose the pivot so that the chance to fall into the worst case performance ($O(n^2)$) is minimized and the average case performance is maximized.

    Example: 'kiniindex',1

    Data Types: double

    Output Arguments

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    kE —k-th order statistic. Scalar

    Element in A that is larger than exactly k - 1 other elements of A.

    varargout —Asor : Partially sorted vector. Vector

    Elements of input vector A(1:k) are sorted in ascending order.

    References

    Riani, M., Perrotta, D. and Cerioli, A. (2015), The Forward Search for Very Large Datasets, "Journal of Statistical Software"

    See Also

    This page has been automatically generated by our routine publishFS