Documentation of sph_grady

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Function Synopsis

y = sph_grady ( z, rx, ry, icos ) ;

Help text

 function y = sph_grady ( z, rx, ry, icos ) ;

 rx and ry must be specified in radian;

 if icos = TRUE; use operator : 1/cos d/dy cos
           else  use operator :       d/dy

 SEE : sph_grad, sph_div, sph_curl

Cross-Reference Information

Listing of function sph_grady

function y = sph_grady ( z, rx, ry, icos ) ;

  global RADUS RADIAN DEGREE

%---- check and reshape input if necessary
  [zy,zx] = size(z); nx = length(rx); ny = length(ry);
  if ( zx ~= nx );
    z = reshape ( z, nx, ny )';
  end;

%---- calculations

  iy2=[2:ny ny]; iy1=[1 1:(ny-1)];

  ady = RADUS * ( ry(iy2) - ry(iy1) )' * ones(size(rx)) ;

  if icos
    % operate as ' 1/cos d/dy cos '
    cosy   = cos( ry' ) * ones(size(rx)) ;
    z      = cosy .* z;
    acosdy = cosy .* ady;
    y      = ( z(iy2,:) - z(iy1,:) ) ./ acosdy;
    % check end points to ensure polar values are reasonable
    if cos(ry( 1))<1e-5; y( 1,:) = mean(y(   2,:)) * ones(1,nx); end
    if cos(ry(ny))<1e-5; y(ny,:) = mean(y(ny-1,:)) * ones(1,nx); end

  else
    % operate as ' d/dy '
    y     = ( z(iy2,:) - z(iy1,:) ) ./ ady;

  end

%---- reshape output if necessary
  if ( zx ~= nx );
    y = reshape ( y', zy, zx );
  end;