MATLAB: Linear fit in Log Scale + extension

curve fittingMATLABplotting

Hello, also this question might be trivial and frequently answered, but yet again I'm not able to grasp it. Long story short, that's what I got:
ind =  f>=5000& f <= 10000 
p = polyfit(f(ind),qU(ind),1);
t = polyval(p,(f(ind)));
plot(f(ind),t,'-r','Linewidth',3);
actually this looks like a straight line to me, even if I set: 
set(gca,'XScale','log')
set(gca,'YScale','log')
However I want to extend this line, lets say to [5000 15000]. How can I finally achieve this? Thx in advance

Best Answer

ind =  f>=5000& f <= 10000 
p = polyfit(f(ind),qU(ind),1);%you will always get a line if degree is 1
x=5000:15000;
t = polyval(p,x);
plot(x,t,'-r','Linewidth',3);
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