fit and function

hi i am a totally new commer . i have a problem to define a function , in principle i guess i did it wrong or there are parts missing would you give a tip how can i write and define a function, at the end i have to define a fit function. best regards clear; Rd=load('LCLS_a-C_sh18_T00202_ex_A1.txt') plot(Rd); hold on; [m,n]=size(Rd); function [y] =uigetfile(Rd) for i=1:m x=1360; w=180; y=(1/2*pi)*(w(i)^2)/(x-x(i))^2+w(i)^2 end end