Z=0.5
m=1.
b=0.2

f(x)=(1.-1./Z)*x+b
g(x)=(1.-m)*x+b

#set xrange[-3:3]

p "sig.inp" u 1:6 w l lw 2

fit[-0.25:0.2] f(x) "sig.inp" u 1:6 via Z,b
fit[-0.25:0.2] g(x) "sig.inp" u 1:6 via m,b

rep f(x)