is there any way for me to apply code to a figure?

Hi i was given a assignment where i was asked to find the Damping ratio from a given figure which is attached i was also told that i had to use Matlab with the code below to find the root zeta but im not sure how i would do that. do i run the code with the figure? im lost on what to do. the error code i get when running the code says it does not recognize Nosc.

fun = @(zeta) (exp((-2*pi*zeta*Nosc)/(sqrt(1-zeta^2))) - Xn_div_X0 );
x0 = [0 1]; %Search bracket for zeta
options = optimset('Display','iter');
[zz, fval, exitflag, output] = fzero(fun,x0,options);

Answer 1

[Matt J]

You can get the x and y data that make up the plot as follows.

h=findobj(gca,'Type','line')
 x=h.XData;
 y=h.YData;

I would imagine that would enable you to do the required analysis.

[jacob booth]

ok when i have the x and y data where would i input it?

[Matt J]

I don't know the formula for the damping ratio, but perhaps if you fit an appropriate curve to x,y you can extract it.

[jacob booth]

this was the given function