Introduction - If you have any usage issues, please Google them yourself
		 
format long
 = uigetfile( *.xls ) 
 file= 
 x=xlsread(file) 
 for i=1:19
 xd1=x(i,1) xd2=x(i,2) xd3=x(i,3) xd4=x(i,4) yd1=x(i,6) yd2=x(i,7) yd3=x(i,8) yd4=x(i,9) 
 m= 
 n= 
 p=polyfit(m,n,1) 
 z=polyval(p,m) 
 poly2sym(p, x ) 
 hold on 
 plot(m,n, o ,m,z)
 end