If your full function is like:
F=(K1/(1+(w/sigma)^2))*0.001+((1j*c1*sigma)/(1+(sigma/w)^2))*0.001;
where F is complex data type
and also the parameters of K1 and c1 are all complex type, then the result will be:
Sum Squared Error (SSE): 330.333035512392
Root of Mean Square Error (RMSE): 3.70996987584576
Correlation Coef. (R): 0.9939271671453
R-Square: 0.987891213589481
Parameter Best Estimate
--------- -------------
k1.realpart 36022.5432052983
k1.imagpart 173011.277144565
c1.realpart 3.85052366252263
c1.imagpart -31.9279234134069
