function vm_parabola=lsqfit_vm_parabola_generator(i_micro_and_N,I_macro)
%this is for being called by lsqcurvefit
%everything is done in terms of samples here

i_micro=i_micro_and_N(1);   N=i_micro_and_N(2);

vm_parabola=I_macro*i_micro - (I_macro.^2)/N;