CURVEMOMENTS is the jOceans module of jLab.

 CURVEMOMENTS  Centroid, area, and many other moments of a closed curve.
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    [XO,YO]=CURVEMOMENTS(XC,YC) returns the centroid of the region bounded 
    by the closed curve specified by the column vectors XC and YC.
 
    [XO,YO,L,R,D]=CURVEMOMENTS(XC,YC) also returns the arc length L, area
    radius R defined such that pi R^2 is the enclosed area, and the root-
    mean-squared distance D from the curve periphery to the centroid.
 
    [XO,YO,L,R,D,A,B,THETA]=CURVEMOMENTS(XC,YC) also returns the region's
    second central moment, the area moment of inertia.  This describes an 
    ellipse with semi-major and minor axes A and B, and orientation THETA. 
 
    The moments are calculated from the curve (XC,YC) using expressions
    for converting spatial to line integrals derived from Green's theorem.
 
    XC and YC may be matrices, with each column specifying a different 
    closed curve.  In this case, all curves must contain the same number 
    of points, corresponding to the rows.  No NaNs may be present. 
    
    XC and YC may also be cell arrays of column vectors.  In this case, the 
    moments will be numerical arrays with the same lengths as XC and YC.
 
    The above figure illustrates an application of CURVEMOMENTS to a
    quasigeostrophic eddy field from QGSNAPSHOT.  The blue curves are
    curves of constant Okubo-Weiss parameter.  These are well matched by
    the red curves, constructed from the second central moment quantites
    A, B, and THETA, and centered at the curve centroids XO, YO.  
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    Velocity moments: Vorticity, angular momentum, kinetic energy, etc.
 
    CURVEMOMENTS can also compute various moments based on the velocity.
 
    [VORT,DIV,MOM,KE]=CURVEMOMENTS(XC,YC,ZC) where ZC is the complex-valued
    velocity ZC=U+iV along the curve, returns the spatially-averaged 
    vorticity VORT, the spatially-averaged divergence MOM, and the angular 
    momentum MOM and kinetic energy KE averaged along the curve periphery.
 
    For the velocity moments, CURVEMOMENTS expects XC and YC to have units
    of km while ZC is in cm/s.  VORT and DIV then have units of 1/s, MOM 
    and MOMSTD have units of cm^2/s, and KE has units of cm^2/s^2.
 
    Note that VORT and DIV are computed as integrals of the tangential and
    normal velocities along the curve, respectively, then converted to area 
    averages by applying Stokes' theorem and the divergence theorem.
 
    MOM is the average angular momentum along the curve with respect to the
    curve centroid. KE is the average value of the kinetic energy along the
    curve, a velocity quantity analagous to averaged squared distance D^2.
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    See also CLOSEDCURVES, CURVEINTERP.
  
    'curvemoments --t' runs some tests.
    'curvemoments --f' generates the above figure.
 
    Usage: [xo,yo]=curvemoments(xc,yc);
           [xo,yo,L,R,D]=curvemoments(xc,yc);
           [xo,yo,L,R,D,a,b,theta]=curvemoments(xc,yc);
           [vort,div,mom,ke,momstd]=curvemoments(xc,yc,zc);
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    This is part of JLAB --- type 'help jlab' for more information
    (C) 2013--20154 J.M. Lilly --- type 'help jlab_license' for details

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