How to display fit equation on plot?

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 1

[G A]

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 2

[Image Analyst]

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)

Answer 3

[GILBERT ALVIOLA]

Something like this... where x and y specifies the position

txt1 = ['y = (' num2str(m) ')x + (' num2str(a) ')']; text(x, y, txt1);

Answer 4

[VBBV]

stress = [0;0.0464;0.1940;0.4962;0.5040;0.5566;0.6040;0.6260;0.6240;0.6100;0.5880;0.5720]; % e.g values
strain = [0;0.2220;0.3600;0.4980;0.5040;0.8820;2.6640;4.4400;5.9100;6.7380;7.1460;7.2900]; % e.g values 
dstrain = gradient(2*strain);
dstress = gradient(2*stress);
estress = stress.*(1+strain)

estress = 12×1

0 0.0567 0.2638 0.7433 0.7580 1.0475 2.2131 3.4054 4.3118 4.7202

estrain = log(1+strain);
p=polyfit(log(dstrain),log(dstress),1);
m=abs(p(1));
b=(((abs(p(2)))));
yy=b.*(strain).^m;
plot(strain,stress,'LineWidth',1.5)
hold on
plot(strain,yy,'r--','LineWidth',2)
hold on
plot(estrain,estress,'-k','linewidth',1.5)
legend('engg stress-strain','exponetial curve fit','true stress-strain')

% axis([.001  .1  40  100])