function [S, lambdai] = CIE_daylight(CCT,lambdai)

% Usage: [S,lambdai] = CIE_daylight(CCT,lambdai)
% CCT (in Kelvin) specifies the correlated colour temperature at which the spectrum is desired
% lambdai (optional) specifies the wavelengths (in nm) at which the spectra is desired
% lambdai should be between 300nm and 830nm

% Author: Kristian Kirk
% Last modified: 9 Aug 2004

load CIE_daylight_basis_S  %%% S0 S1 S2 lambda_S

if nargin < 2
    lambdai = lambda_S;
else
    S0 = interp1( lambda_S, S0, lambdai, 'linear' )';
    S1 = interp1( lambda_S, S1, lambdai, 'linear' )';
    S2 = interp1( lambda_S, S2, lambdai, 'linear' )';
end

[w1,w2] = CIE_daylight_weights(CCT);

S = ([S0 S1 S2]*[ones(size(w1)); w1; w2]);
lambdai = lambdai';