%
% V = volbet2iso(TRACER,LIMITS,DEPTH,LAT,LONG)
%
% This function computes the ocean volume between two 2 iso surfaces,
% given fixed limits eastward, westward and southward.
%
% TRACER = TRACER(DEPTH,LAT,LONG) : surface tracer variable in 3D
% LIMITS = [OUTCROP1 OUTCROP2 MAX_DEPTH MAX_LAT1 MAX_LAT2 MAX_LONG1 MAX_LONG2]
%          : limit's values (MAX_DEPTH and MAX_LAT2 are used only if
%            the iso-outcrop's surfaces reach them).
% DEPTH                           : vertical axis (1D), m downward, positive
% LAT                             : latitude axis (1D), degrees northward
% LONG                            : longitude axis (1D), degrees east
% V                               : single volume value (m^3)
%
% 06/12/2006
% gmaze@mit.edu
% 


function varargout = volbet2iso(TRACER,LIMITS,DEPTH,LAT,LONG)


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% PRE-PROCESS and ERROR CHECK %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% Check number of input:
if nargin ~= 5 
  help volbet2iso.m
  error('volbet2iso.m : Wrong number of parameters')
  return
end %if
  
% Check dimensions:
n = size(TRACER);
if length(n)==3
  [nz ny nx] = size(TRACER);
  if nz~=length(DEPTH) | ny~=length(LAT) | nx~=length(LONG)
     help volbet2iso.m
     error('volbet2iso.m : Axis must have same dimensions than TRACER field');
     return
  end %if
else
  help volbet2iso.m
  error('volbet2iso.m : TRACER must be a 3D field')
  return
end %if

% Ensure that axis are of dim: (1,N) and well sorted (increasing values):
a=size(DEPTH);
if a(1) ~= 1,  DEPTH=DEPTH'; end 
S = sort(DEPTH);
if S ~= DEPTH
  help volbet2iso.m
  error('volbet2iso.m : DEPTH must be increasing values')
  return
end %if
a=size(LAT);
if a(1) ~= 1,  LAT=LAT'; end 
S = sort(LAT);
if S ~= LAT
  help volbet2iso.m
  error('volbet2iso.m : LAT must be increasing values')
  return
end %if
a=size(LONG);
if a(1) ~= 1,  LONG=LONG'; end 
S = sort(LONG);
if S ~= LONG
  help volbet2iso.m
  error('volbet2iso.m : LONG must be increasing values')
  return
end %if

% LIMITS definition:
if length(LIMITS) ~=7
  help volbet2iso.m
  error('volbet2iso.m : LIMITS must contains 7 values')
  return
end %if
OUTCROPS = sort( LIMITS(1:2) );
H_MAX    = LIMITS(3);
LAT_MAX  = sort( LIMITS(4:5) );
LONG_MAX = sort( LIMITS(6:7) ); 


  
%%%%%%%%%%%%%%%%%%
% COMPUTE VOLUME %
%%%%%%%%%%%%%%%%%%
% It's computed as the difference between the northern outcrop volume
% and the southern outcrop one.
[V1 V1mat dV1] = subfct_getvol(TRACER,DEPTH,LAT,LONG,[OUTCROPS(1) H_MAX LAT_MAX LONG_MAX]);
[V2 V2mat dV2] = subfct_getvol(TRACER,DEPTH,LAT,LONG,[OUTCROPS(2) H_MAX LAT_MAX LONG_MAX]);


% Then:
V = max(V1,V2)-min(V1,V2);



%%%%%%%%%%%
% OUTPUTS %
%%%%%%%%%%%
switch nargout
 case 1
  varargout(1) = {V};
 case 2
  varargout(1) = {V};
  varargout(2) = {V1mat};
 case 3
  varargout(1) = {V};
  varargout(2) = {V1mat};
  varargout(3) = {dV1};
end %switch nargout