%Energien von NIST
%https://www.physics.nist.gov/PhysRefData/XrayTrans/Html/search.html

%Mo Kalpha1 = 17.48 keV
%Mo Kbeta1  = 19.61 keV
%Au Lalpha1 =  9,71 keV
%Au Lbeta1  = 11,44 keV
format long;

ch = [144; 169; 254; 284];
E = [9.71; 11.44; 17.48; 19.61];

plot(ch, E, '+');
hold on;

ft = fittype( @(a, b, x) a.*x+b);
[curve, gof] = fit(ch, E, ft, 'Start', [0.07, -0.44])
plot(curve);