function Xout = avgoasis(Xin, Lon, TimeLim)
% AVGOASIS - Create a daily average of data in oasis files
%
% Use as: avgoasis(X, Lon, TimeLim)
%         avgoasis(X)            % No accounting offset, use data between 10am and 2pm
%         avgoasis(X,[], TimeLim)% No accounting offset, specify TimeLims
%         avgoasis(X,[])         % No accounting offset, use data between 10am and 2pm
%
% Inputs: X   = matrix of data (from READOASIS), 1st column is julian day,
%             last column is year.
%         Lon = Longitude of readings (scalar) used to calculate the offset
%             from GMT. Default = 'no GMT offset
%         TimeLims = 2 element vector of hours to average between. Default = [10 14]
%             This feature is used for spectral data. 
%             It may also be a scalar (fractional day) in which case the Local noon is calcualted by
%             using NOON_. Then TimeLim specifies the time on either side of noon to average between. 
%
% Outputs: Xo = daily average of column wise data.
%
% Requires: GMTOFFSET, JUL2DATE, Oceans toolbox

% Brian Schlining
% 17 May 1999


if nargin < 2 | isempty(flag) | isnan(flag)
   Lon = 0;
end

%=========================================
% Error Checking on the TimeLims argument
%=========================================
if nargin < 3                             % Default
   StartTime = 10;
   EndTime   = 14;
else
   if length(TimeLim) > 1
      if TimeLim(1) > TimeLim(2)
         error('AVGOASIS: TimeLims must be [smaller larger]')
      end
      if TimeLim(2) > 24 | TimeLim(1) < 0
         error('AVGOASIS: Invalid Time limit')
      end
      StartTime = TimeLim(1);
      EndTime   = TimeLim(2);
      Flag = 0;
   else
      Flag = 1;
   end
   
   
   
end

switch Lon
case 0
   Offset = 0;
otherwise
   Offset = gmtoffset(Lon)            % Calculate the ofset in days from GMT
end

%===================================
% Get the date number of each point
%===================================
d        = jul2date(Xin(:,1),Xin(:,end));          % Convert Julian day to matlab's format
GoodDate = find(~isnan(d));
d        = d(GoodDate);
Xin      = Xin(GoodDate,:);
[d, DateOrder] = sortrows(d);           % Make sure the data is sorted by time
Xin      = Xin(DateOrder,:);
[Year, Month, Day, Hour, Minute, Second] = datevec(d + Offset);


n = 1;                                 % Counter for the start of each 15 minute data set
m = 1;                                 % The position we're writing the data to
[NumOfPoints NumOfFields] = size(Xin);
Xout = ones(size(Xin))*NaN;            % Preallocate memory


fprintf(1,'(AVGOASIS)')
OK = 1;      
while OK
   %======================================================
   % Create a daily average for data between 10am and 2pm
   %======================================================
   
   % Find all data points between 10:00 and 14:00 for each day
   j = find(Year == Year(n) & Month == Month(n) & Day == Day(n) & ...
      Hour >= StartTime & Hour <= EndTime);
   
   % Move pointer to the next day
   k = find(Year == Year(n) & Month == Month(n) & Day == Day(n));
   
   if ~isempty(j)
      % Get the data that occurs during each minute, take its average and then 
      % write it out to the new structure, OUT.
      if length(j) == 1
         Xout(m,:) = Xin(j,:);
      else
         Xout(m,:)  = nanmean(Xin(j,:));
      end
      n = n + length(k);
      m = m + 1;
   elseif isempty(j) & ~isempty(k)
      n = n + length(k)';
   else
      n = n + 1;
   end
   
   if ~rem(m,200)
      fprintf(1,'.')
   end
   
   if n > NumOfPoints
      fprintf(1,'\n')
      % Remove all the trailing NaN's before returning OUT
      NotNaN = find(~isnan(Xout(:,1)));
      Xout = Xout(NotNaN,:);
      return
   end
end