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ep2ap

PURPOSE ^

SYNOPSIS ^

function [Au, PHIu, Av, PHIv, w, TWOCIR]=ep2ap(SEMA, ECC, INC, PHA, plot_demo)

DESCRIPTION ^

 Convert tidal ellipse parameters into amplitude and phase lag parameters.
 Its inverse is app2ep.m. Please refer to app2ep for the meaning of the 
 inputs and outputs.

 Zhigang Xu
 Oct. 20, 2000

 Document:  tidal_ellipse.ps

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [Au, PHIu, Av, PHIv, w, TWOCIR]=ep2ap(SEMA, ECC, INC, PHA, plot_demo)
0002 %
0003 % Convert tidal ellipse parameters into amplitude and phase lag parameters.
0004 % Its inverse is app2ep.m. Please refer to app2ep for the meaning of the
0005 % inputs and outputs.
0006 %
0007 % Zhigang Xu
0008 % Oct. 20, 2000
0009 %
0010 % Document:  tidal_ellipse.ps
0011 %
0012 if nargin < 5
0013      plot_demo=0;  % by default, no plot for the ellipse
0014 end
0015 
0016    Wp = (1+ECC)/2 .*SEMA;
0017    Wm = (1-ECC)/2 .*SEMA;
0018    THETAp = INC-PHA;
0019    THETAm = INC+PHA;
0020 
0021    %convert degrees into radians
0022    THETAp = THETAp/180*pi;
0023    THETAm = THETAm/180*pi;
0024 
0025    %Calculate wp and wm.
0026    wp = Wp.*exp(i*THETAp);
0027    wm = Wm.*exp(i*THETAm);
0028    
0029    if nargout >= 5
0030       ndot=36;
0031       dot = 2*pi/ndot;
0032       ot = [0:dot:2*pi-dot];
0033       w = wp(:)*exp(i*ot)+wm(:)*exp(-i*ot);
0034       w=reshape(w, [size(wp) ndot]);
0035    end
0036 
0037    % Calculate cAu, cAv --- complex amplitude of u and v
0038    cAu = wp+conj(wm);
0039    cAv = -i*(wp-conj(wm));
0040    Au  = abs(cAu);
0041    Av  = abs(cAv);   
0042    PHIu = -angle(cAu)*180/pi;
0043    PHIv = -angle(cAv)*180/pi;
0044    
0045    % flip angles in the range of [-180 0) to the range of [180 360).
0046    id = PHIu < 0; PHIu(id) = PHIu(id) + 360;
0047    id = PHIv < 0; PHIv(id) = PHIv(id) + 360;
0048 
0049   if any(plot_demo)   
0050      plot_ell(SEMA,ECC,INC,PHA,plot_demo);
0051   end
0052 
0053   if nargout == 6
0054       TWOCIR=struct('Wp', Wp, 'THETAp', THETAp, 'wp', ... 
0055             wp, 'Wm', Wm, 'THETAm', THETAm, 'wm', wm, 'ot', ot, 'dot', dot);
0056  end
0057   
0058 %Authorship Copyright:
0059 %
0060 %    The author of this program retains the copyright of this program, while
0061 % you are welcome to use and distribute this program as long as you credit
0062 % the author properly and respect the program name itself. Particularly,
0063 % you are expected to retain the original author's name in this original
0064 % version of the program or any of its modified version that you might make.
0065 % You are also expected not to essentially change the name of the programs
0066 % except for adding possible extension for your own version you might create,
0067 % e.g. app2ep_xx is acceptable.  Any suggestions are welcome and enjoy my
0068 % program(s)!
0069 %
0070 %
0071 %Author Info:
0072 %_______________________________________________________________________
0073 %  Zhigang Xu, Ph.D.
0074 %  (pronounced as Tsi Gahng Hsu)
0075 %  Research Scientist
0076 %  Coastal Circulation
0077 %  Bedford Institute of Oceanography
0078 %  1 Challenge Dr.
0079 %  P.O. Box 1006                    Phone  (902) 426-2307 (o)
0080 %  Dartmouth, Nova Scotia           Fax    (902) 426-7827
0081 %  CANADA B2Y 4A2                   email xuz@dfo-mpo.gc.ca
0082 %_______________________________________________________________________
0083 %
0084 %Release Date: Nov. 2000
0085 
0086

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