>> TGS_phase_analysis('V_single_crystal-2019-06-30-06.40um-85degrees#3-POS-1.txt','V_single_crystal-2019-06-30-06.40um-85degrees#3-NEG-1.txt',6.4,1)

f2 = 

     General model:
     f2(x) = A.*(erfc(q*sqrt(k*(x+start_time)))-beta*exp(-q^2*k*(x+start_time)
                    )./sqrt((x+start_time)))+B.*sin(2*pi*(peak_freq)*(x+
                    start_time)+p)*exp(-(x+start_time)/t)+D
     Coefficients (with 95% confidence bounds):
       A =     0.08351
       k =    1.07e-05
       beta =   1.076e-05
       B =    0.009938
       p =      0.3397
       t =   1.002e-10  (fixed at bound)
       D =  -0.0004501  (-0.00117, 0.0002699)
     Problem parameters:
       q =   9.817e+05
       start_time =    1.25e-09
       peak_freq =   3.963e+08
Bad fit for:V_single_crystal-2019-06-30-06.40um-85degrees#3-POS-1.txt~re: alpha

ans =

   3.9626e+08