I was trying to make a best-fit line with the data that I have, but for some reason the polyfit command doesn't seem to give me the right answer for it. Does anyone know how to fix it? Thank you.
thickness = 0.8; % the units are in mm
width = 12.7;area = thickness*width;load = xlsread('homework1.xlsx','A9:A42');strain = xlsread('homework1.xlsx','B9:B42');trueStress1 = (load.*(1+strain))./area; % true stress calculation
trueStrain1 = log(strain + 1); % true strain calculation
x = log(trueStrain1);y = log(trueStress1);p = polyfit(x,y,1); % bestfit the line between points
f = polyval(p,x); figure;plot(x,y,'o');hold onplot(x,f,'-');title('True Stress vs. True Strain');xlabel('Log \epsilon');ylabel('Log \sigma');legend('data','linear fit','location','northwest')
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