function PSF = PSFip(phi, age, p, m)
%PSFip(phi, age, p, m)	Calculates the pointspread function (PSF) based on the 
%	equations espoused by Ijspeert et al. The user must specify the angle,
%	phi, in degrees. All other values are optional, and will be set at the 
%	following defaults if not specified:
%
%	age = age of subject in years 	Default age = 0 years	
%	p = pupil diameter in mm 		Default value = 4 mm.
%	m = pigmentation parameter		Default = call to pigment function
%

switch nargin
	case{nargin<1}
		error 'too few arguments'
	case{1}
		age = 0;
		p = 4;
		m = pigment;	
	case{2}
		p = 4;
		m = pigment;
	case{3}
		m = pigment;
	case{4}
	
	case{nargin>=5}
		error 'too many arguments'
end

AF = agefact(age);

%c and Fbi calculations for given i 
for i=1:4
	switch i
		case{1}
		c1 = c1calc(AF, p, m); 
		fBi1 = funBi(i, phi, p, AF, m);			
		case{2}
		c2 = c2calc(AF, p, m);	
		fBi2 = funBi(i, phi, p, AF, m);
		case{3}
		c3 = c3calc(AF, m);
		fBi3 = funBi(i, phi, p, AF, m);
		case{4}
		c4 = c4calc(AF, m);
		fBi4 = funBi(i, phi, p, AF, m);
	end
end
%Normalization of c to sum to 1
ctotal = (c1 + c2 + c3 + c4);

%PSF calculations
PSF1 = (c1/ctotal) * fBi1;
PSF2 = (c2/ctotal) * fBi2;
PSF3 = (c3/ctotal) * fBi3;
PSF4 = (c4/ctotal) * fBi4;

%Addition of the four final components
PSF = PSF1 + PSF2 + PSF3 + PSF4;