Asked by Christopher
on 17 Nov 2013

Hello all,

I have written code that creates a power fit to some data. The code is :

p=polyfit(log(pla_strain),log(pla_stress),1); m=p(1); b=exp(p(2)); yy=b.*(pla_strain).^m;

I think plot the data with the fit as follows:

loglog(pla_strain,pla_stress,'LineWidth',4) hold on plot(pla_strain,yy,'r--','LineWidth',2) axis([.001 .1 40 100]) hold off

My problem is I am trying to display the equation of the fit on the plot. The equation is of the form y=b*x^m where b and m are the two coefficients from the polyfit. I would like to display this equation in the same location of the plot every time, which would ideally be towards the top center.

Thanks

Answer by G A
on 18 Nov 2013

txt1='b*x^m'; yL=get(gca,'YLim'); xL=get(gca,'XLim'); text((xL(1)+xL(2))/2,yL(2),txt1,... 'HorizontalAlignment','left',... 'VerticalAlignment','top',... 'BackgroundColor',[1 1 1],... 'FontSize',12);

Answer by Image Analyst
on 18 Nov 2013

You're going to have to convert the x and yy back into pla_strain and pla_stress so you can plot them

x = log(pla_strain); pla_strain_fitted = exp(x); yy = m .* x + b; % This equals log(pla_stress) pla_stress_fitted = exp(yy); loglog(pla_strain_fitted, pla_stress_fitted, 'LineWidth',4)

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