f_nu

 fnu=f_nu(nu)

 spectral dependence of CMB, as in Holder 2003
 f_nu(x).
 
 x is dimensionless frequency x=(h*nu)/(k*T)

 e.g.

 nu=[1:1:300]*1e9;
 plot(nu,f_nu(nu));

0001 function fnu=f_nu(nu)
0002 % fnu=f_nu(nu)
0003 %
0004 % spectral dependence of CMB, as in Holder 2003
0005 % f_nu(x).
0006 %
0007 % x is dimensionless frequency x=(h*nu)/(k*T)
0008 %
0009 % e.g.
0010 %
0011 % nu=[1:1:300]*1e9;
0012 % plot(nu,f_nu(nu));
0013 
0014 h=6.626e-34;
0015 k=1.38e-23;
0016 T=2.726;
0017 
0018 x=(h*nu)/(k*T);
0019 
0020 fnu=(x.^4).*exp(x).*(exp(x)-1).^-2.*(x./tanh(x/2)-4);
0021 
0022 return