function varargout = TEmodes(m,p,varargin);
%nu_mp = TEMODES(m,p) with no options returns the Bessel 
%  root nu_mp for the given cylindrical Tranverse Electric 
%  mode indicies, 'm' and 'p', where 'm' is the azimuthal 
%  variation and 'p' is the radial variation (axial 
%  variations are assumed to be unity).  Both 'm' and 'p' 
%  must be integers.  A null [] is returned if a mode was 
%  not found in the table.
% 
%nu_mp = TEMODES(m,p, 'OPTIONS', OPTION_ARG) performs functions 
%  defined by the OPTIONS string:
%
%  OPTIONS:     OPTION_ARG:   Function:
% 'neighbors'  an integer N   Returns a vector of the closest 2N 
%                             Bessel roots to the {mp} combination.
%
% 'family'     an integer N   Returns a vector of the closest 2N+1
%                             roots including the central root.
%
%  If the limits of the table have been reached, the nu_mp vector 
%  size decreases accordingly.
%
%[nu,mp] = TEMODES( ... ) returns roots in 'nu', and returns a 
%  matrix 'mp' consisting of the 'm' root(s) in the first column
%  and the corresponding 'p' root(s) in the second column.
%
%[nu,m,p] = TEMODES( ... ) returns roots in 'nu', a column vector of 
%  m-index/-ices in 'm' and a column vector of p-index/-ices in 'p'.
% 
%
%-------------------------------
% Example:
%    temodes(0,4,'family',2)  
%
% Returns:
%    12.9324
%    13.1704
%    13.3237
%    13.8789
%    13.9872
%-------------------------------
%
% NOTE: requires the 'nu_TE.txt' data file, which stores root values.
%
% Last edit by Colin Joye, 8/19/03T

% load TE roots table
V = load('nu_TE.txt');

% find the locations of the roots in the table:
M = find(V(:,1)==m);
P = find(V(:,2)==p);
if( isempty(M) | isempty(P) ),
  nu_mp = [];
  disp(['Error: TE_{' int2str(m) ',' int2str(p) '} mode not found.']);
  break;
end

% make matrices for comparison
Sm = ones(length(P),1)*M';
Sp = P*ones(1,length(M));

% find location where m and p coincide
loc = Sm( ind2sub( size(Sm),find( Sm==Sp ) ) );

% check for input arguments
if nargin > 3,
N = [];
% search for 'neighbors' option
n = find( strcmp( 'neighbors',varargin ) == 1);
if ~isempty(n) 
  N     = varargin{n+1};
  % create vector of neighboring root locations.
  loc = [loc-N:(loc-1) (loc+1):loc+N];
end
% search for 'family' option
n = find( strcmp( 'family',varargin ) == 1);
if ~isempty(n) 
  N     = varargin{n+1};
  % create vector of neighboring root locations.
  loc = [loc-N:loc+N];
end
if isempty(N),
  disp(['Error, unknown options found']);
  break;
end
max = size(V,1);
% make sure we stay within index limits
loc = loc( find(loc > 0 & loc < max) );
nu_mp = V(loc,3);

else % no varargs were given, just return one root.
  nu_mp = V(loc,3);
end

% return the right number of outputs
switch(nargout)
case {0,1}
  varargout = {nu_mp};
case {2}
  varargout = {nu_mp,[V(loc,1) V(loc,2)]};
case {3}
  varargout = {nu_mp,V(loc,1),V(loc,2)};
otherwise
  disp('Error in TEMODES.m, wrong number of outputs');
  break;
end
% --- END TEmodes.m ----------------