function [lon] = CN_assign( ref, Yr, lon_w, lon_e, lat_s, lat_n, Rain250Name, CN250_unassigned, CN250_assigned, season_code)


formatIn = 'dd mmm yyyy';
startday = datenum(['1-jan-',num2str(Yr)], formatIn);
endday = datenum(['31-dec-',num2str(Yr)], formatIn);


D =(startday:endday)'; 
L = (1:yeardays(Yr));


% create season (dormant & growing) array
season = NaN((yeardays(Yr)),1);
% 1 is dormant season, 2 growing season
% set all of 'season' to dormant season
%season_code = string(table2array(t(18,2)));
season(:,:) = season_code;

%% Global Curve Number (gcn) - clip lon and lat to limits; assume ARCI, ARCII, ARCIII have same extents
%load longitude array; Global Curve Number (gcn)
lon_gcn = double(ncread(Rain250Name,'longitude'));
% load latitude array; Global Curve Number (gcn)
lat_gcn = double(ncread(Rain250Name,'latitude'));
% determine which indices correspond to dimension 1: Global Curve Number (gcn)
ind1_gcn = find(lon_gcn>= lon_w & lon_gcn <= lon_e);
% determine which indices correspond to dimension 2: Global Curve Number (gcn)
ind2_gcn = find(lat_gcn>= lat_s & lat_gcn <= lat_n);
% Clip lat and lon to their specified range
lat_gcn = lat_gcn(ind2_gcn);
lon_gcn = lon_gcn(ind1_gcn);


%% Output NC file, create variables and write attributes
% create variable to hold Curve Number 
nccreate(CN250_assigned, 'CurveNumber', 'Dimensions',{'longitude',length(lon_gcn), 'latitude',length(lat_gcn),'time', (Inf)},'DataType', 'int8');
ncwriteatt(CN250_assigned, 'CurveNumber', "units", ("dimentionless"));

% create dimensions
nccreate(CN250_assigned, 'longitude', 'Dimensions',{'longitude', length(lon_gcn)}); % longitude
nccreate(CN250_assigned, 'latitude', 'Dimensions',{'latitude', length(lat_gcn)}); % latitude
nccreate(CN250_assigned, 'time', 'Dimensions',{'time', Inf}); % create time dimension

% Output NC file, write dimensions
ncwrite(CN250_assigned, 'longitude', lon_gcn); % write longitude dimension
ncwrite(CN250_assigned, 'latitude', lat_gcn); % write latitude dimension
ncwrite(CN250_assigned, 'time', D); % write time

%% Calculate Curve Number 
% read Global Curve Number data
ARCI = int8(ncread(CN250_unassigned, 'GCN_ARCI', [ind1_gcn(1), ind2_gcn(1)], [length(ind1_gcn), length(ind2_gcn)]));
ARCII = int8(ncread(CN250_unassigned, 'GCN_ARCII', [ind1_gcn(1), ind2_gcn(1)], [length(ind1_gcn), length(ind2_gcn)]));
ARCIII = int8(ncread(CN250_unassigned, 'GCN_ARCIII', [ind1_gcn(1), ind2_gcn(1)], [length(ind1_gcn), length(ind2_gcn)]));
cn = int8(ones(length(lon_gcn), length(lat_gcn))*127);

for i=1:yeardays(Yr)
    
    
    cn = int8(ones(length(lon_gcn), length(lat_gcn))*127);
    % read NC file
    rs = int16(ncread(Rain250Name, 'RainSum250', [ind1_gcn(1), ind2_gcn(1), i], [length(ind1_gcn), length(ind2_gcn), 1]));
    if season(i,1) == 1 % DORMANT season
        dry = find(rs<13); % dry 
        cn(dry) = ARCI(dry); % set Curve Number
        clear dry; 
        norm = find(rs>=13 & rs<=28); % normal
        cn(norm) = ARCII(norm); % set Curve NUmber 
        clear norm
        wet = find(rs>28); % wet
        cn(wet) = ARCIII(wet); % set curve number
        clear wet;
    elseif season(i,1) == 2 % GROWING season
        dry = find(rs<36); % dry 
        cn(dry) = ARCI(dry); % set curve number
        clear dry;
        norm = find(rs>=36 & rs<=53); % normal
        cn(norm) = ARCII(norm); % set curve number
        clear norm;
        wet = find(rs>53); % wet
        cn(wet) = ARCIII(wet); % set curve number
        clear wet;
    end
    % write to NC file
    ncwrite(CN250_assigned, 'CurveNumber', cn, [1 1 i]);
    clear cn;
end
% Reference: Silveira, et al., (2000) https://doi.org/10.1080/02626660009492302
% Total 5-day antecedent rainfall (mm)
% for DORMANT season; Dry less than 13; normal 13 to 28; wet more than 28.
% for GROWING season; Dry less than 36; normal 36 to 53; wet more than 53.


end

% created by robert g. delaney (2023)
% This work is licensed under the Creative Commons Attribution-% % NonCommercial-ShareAlike 4.0 International License. 
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