function OUT = prc_ed490(IN)
% PRC_ED490 - Estimate Edx from Ed490
%
% PRC_ED490 estimates the downwelled iradiance (Ed) for 412 (nm), 443, 510, 555, 656, 
% and PAR from measured values of Ed490. The relationships between irradiances are
% derived from linear regressions of data from the equatorial pacific near local noon.
% Contact Peter Strutton or Brian Schlining for details on the methods.
%
% Use as: OUT = prc_ed490(IN)
% Inputs: IN = Data structure created by READOUT
% Output: OUT = Data structure with all fields in IN and the following additional fields:
%               ED_412, ED_443, ED_510, ED_555, ED_656, ED_670, ED_683, and ED_PAR

% Brian Schlining
% 20 Jan 1999

% Caluculate Irradiances from regression equations
IN.ED_412 = 0.57092 .* IN.ED_490 - 1.9642;      % From Satlantic
IN.ED_443 = 0.89835 .* IN.ED_490 - 1.9474;      % From Satlantic
IN.ED_510 = 1.00710 .* IN.ED_490 - 1.3556;      % From Satlantic
IN.ED_555 = 0.93837 .* IN.ED_490 - 0.96641;     % From Satlantic
IN.ED_656 = 0.813   .* IN.ED_490 + 8.455;       % From Eqpac Mooring
IN.ED_670 = 0.78515 .* IN.ED_490 - 0.45482;     % From Satlantic
IN.ED_683 = 0.77745 .* IN.ED_490 - 0.66826;     % From Satlantic
IN.ED_PAR = 0.00126 .* IN.ED_490 + 0.0048;      % From Eqpac Mooring

% Set negative values to NaN
%i = find(IN.ED_412 < 0);IN.ED_412(i) = NaN;
%i = find(IN.ED_443 < 0);IN.ED_443(i) = NaN;
%i = find(IN.ED_510 < 0);IN.ED_510(i) = NaN;
%i = find(IN.ED_555 < 0);IN.ED_555(i) = NaN;
%i = find(IN.ED_656 < 0);IN.ED_656(i) = NaN;
%i = find(IN.ED_670 < 0);IN.ED_670(i) = NaN;
%i = find(IN.ED_683 < 0);IN.ED_683(i) = NaN;
%i = find(IN.ED_PAR < 0);IN.ED_PAR(i) = NaN;



OUT = IN;