RESU = [
20,-9.7957;
21.9995,-9.7713;
23.9998,-9.758;
24.0001,-9.7513;
25.9999,-9.7368;
26,-9.7298;
29.9996,-9.6904;
34.9998,-9.6234;
35,-9.6164;
39.9998,-9.5417;
40,-9.5493;
50.0002,-9.3761;
77.17,-8.754;
90.0001,-8.4044;
149.9992,-6.2687;
199.9988,-3.9821;
273.15,0.001;
372.7,6.332]


// 5 parameters
function y = curve(x,coef)
  A4 = coef(1)
  A3 = coef(2)
  A2 = coef(3)
  A1 = coef(4)
  A0 = coef(5)
  y  = (A4*(x^4)) + (A3*(x^3)) + (A2*(x^2)) + (A1*x) + A0
endfunction  


// function descriptor
function e = G(parameters,test)
  x_test = test(1)
  y_test = test(2)
  e = y_test - curve(x_test,parameters) 
endfunction


// Solve the problem
parameters_init = [0.1 ; 0.1 ; 0.1 ; 0.1 ; 0.1]
[parameters_opti,err] = datafit(G,RESU',parameters_init)


// Drawing of the experimental data & the fitted curve
y_calc = zeros(Line_number,1);
for i = 1 : Line_number
  y_calc(i,1) = curve(RESU(i,1),parameters_opti);
end;

clf(0)
plot2d(RESU(:,1),RESU(:,2),style=-2)     
plot2d(RESU(:,1), y_calc, style = 2)
legend(["Experimental data", "fitted curve"],2);