TWODMED is the jStats module of jLab.

 TWODMED  Median value of a function of two variables.
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    MED=TWODMED(X,Y,Z,XBIN,YBIN) where X, Y and Z are arrays of the same
    length, forms the median of Z over the XY plane.
 
    If XBIN and YBIN are length N and M, respectively, then MED is of 
    size M-1 x N-1.  Bins with no data are assigned a value of NAN.
 
    XBIN and YBIN must be monotonically increasing. 
 
    MED=TWODMED(X,Y,Z,N) uses N bins in the X and Y directions, linearly
    spaced between the minimum and maximum values.  MED is N-1 x N-1.
 
    MED=TWODMED(X,Y,Z,[XMIN XMAX],[YMIN YMAX],N) uses N bins, linearly
    spaced between the designated X and Y values.  MED is N-1 x N-1. 
 
    [MED,XMID,YMID]=TWODMED(...) optionally returns the midpoints XMID
    and YMID of the bins.
 
    X, Y, and Z can also be cell arrays of numerical arrays, in which case 
    all data values are concatented prior to finding the histogram.
 
    TWODMED, TWODSTATS, and TWODHIST 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. 
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    Algorithms
 
    TWODMED uses a fast (exact) algorithm which is particularly efficient 
    for large arrays.
 
    The values of Z are sorted into bins according to the associated (X,Y)
    value, with bin edges specified by XBIN and YBIN, and the median of 
    finite values of Z in each bin is computed looplessly using indexing.
 
    TWODMED(...,'slow') uses a slow algorithm which uses less memory.  
    By default, TWODMED uses a fast but memory-intensive algorithm.  
    Use this flag if you get an out-of-memory error.
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    See also TWODHIST, TWODSTATS.
    
    'twodmed --f' generates the sample figure shown above.
    'twodmed --t' runs a test.
 
    Usage: med=twodmed(x,y,z,N);
           med=twodmed(x,y,z,[xmin xmax],[xmin xmax],N);
           med=twodmed(x,y,z,xbin,ybin);
           [med,xmid,ymid]=twodmed(x,y,z,xbin,ybin);
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    This is part of JLAB --- type 'help jlab' for more information
    (C) 2007--2015 J.M. Lilly --- type 'help jlab_license' for details