TWODHIST is the jStats module of jLab.

 TWODHIST  Two-dimensional histogram.
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    MAT=TWODHIST(X,Y,XBIN,YBIN) where X and Y are arrays of the same
    length, creates a two-dimensional histogram MAT with bin edges
    specified by XBIN and YBIN. 
 
    If XBIN and YBIN are length N and M, respectively, then MAT is of
    size M-1 x N-1.  XBIN and YBIN must be monotonically increasing. 
 
    [MAT,XMID,YMID]=TWODHIST(...) optionally returns the midpoints XMID
    and YMID of the bins.
 
    TWODHIST, TWODSTATS, and TWODMED are three related functions for 
    computing statistics as a function two variables using very fast
    algorithms that avoid any loops through efficient use of indexing.
 
    X and Y can also be cell arrays of numerical arrays, in which case 
    all data values are concatented prior to finding the histogram.
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    Automatic bin calculation
 
    TWODHIST can compute appropriate bins internally.
 
    [MAT,XMID,YMID]=TWODIST(X,Y,N) uses N bins in the X and Y directions,
    linearly spaced between the minimum and maximum values, and returns the
    bin midpoints in XMID and YMID.  MAT is N-1 x N-1.
 
    [MAT,XMID,YMID]=TWODIST(X,Y,[XMIN XMAX],[YMIN YMAX],N) similarly uses N
    bins, linearly spaced between the designated X and Y values.  
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    Algorithms
 
    By default, TWODHIST now works with an internal call to Matlab's
    HISTCOUNTS2 function, available as of Matlab 2015b.  This is much 
    faster than the previous algorithm.
 
    If HISTCOUNTS2 is not available, TWODHIST uses loopless algorithm that
    is in turn much faster than an explicit loop.  TWODHIST(...,'jLab') 
    uses this algorithm, while TWODHIST(...,'slow') uses the explicit loop.
    These options are mostly used for testing purposes.
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    Parallelization
 
    TWODHIST(...,'parallel') parallelizes the computation using the fast 
    algorithm together with SPMD.  This requires that Matlab's Parallel
    Computing Toolbox be installed.  While TWODHIST is already very fast,
    parallelization may be useful for extremely large datasets.
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    See also TWODMED, TWODSTATS.
 
    'twodhist --f' generates the sample figure shown above.
    'twodhist --t' runs some tests.
 
    Usage: [mat,xmid,ymid]=twodhist(x,y,N);
           [mat,xmid,ymid]=twodhist(x,y,[xmin xmax],[ymin ymax],N);
           mat=twodhist(x,y,xbin,ybin);
           [mat,xmid,ymid]=twodhist(x,y,xbin,ybin,'parallel');
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    This is part of JLAB --- type 'help jlab' for more information
    (C) 2004--2015 J.M. Lilly --- type 'help jlab_license' for details    

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