How to extract y-value data at a certain x-value?

I would like to take all the y values from the attached figure that incercept the x data value of 5x10^5 Hz and then re-create this figure but instead Velocity against Resonator length. Is there a way to do this?

thank you

[KSSV]

How did you plot that figure? Do you have coordinates of each curve?

[aman verma]

It was done with lines of code. I can upload the code if that makes it easier.

[KSSV]

Yes...it is better to show us the code.

[aman verma]

%% set the elastic constants for the aluminium
E_al=70e9;
mu_al=26e9;
K_al=76e9;
nu_al=0.35;
rho_al=2700;
lambda_al=K_al-2*mu_al/3;

%% set the parameters for the substrate
L=2e-3; % m Lattice spacing
rho=rho_al; % Kg/m^3
mu=mu_al; % Pa shear modulos
lambda=lambda_al; % Pa Lame parameter
E=mu.*(3.*lambda+2.*mu)/(lambda+mu)

E = 7.0016e+10

E=E_al;
Cl=sqrt((lambda+2*mu)./rho);
Ct=sqrt(mu./rho);
nu=lambda./(2.*(lambda+mu));
nu=nu_al;
neta_R=(0.87+1.12.*nu) ./ (1+nu);
CR=Ct*neta_R;

%% set the parameters for the rods / resonators
rho_r=rho_al; % Kg / m^3
mu_r=mu_al; % Pa
lambda_r=lambda_al; % Pa
E_r=E_al;
%h=(L/2-0.5e-3);%0.3e-3; % m resonator diameter
h=0.5e-3;
%l=10e-3; % m resonator length
S=pi.*(h/2)^2; % m^2 resonator area

% shear mode velocity = sqrt(mu/rho);
% longitudanal velocity = sqrt((lambda+2mu)/rho);
r=sqrt(1./(2+mu/lambda));

%% compute bandgaps equation 3.28 - I use this to divide the solution space between the bandgaps
figure;
for x=linspace(0.001,0.01,100)
	l=x;
	alpha_r=sqrt(rho_r./E_r);
	w1=(1./(l.*alpha_r)).*(1*pi-atan(L^2./(S.*sqrt(1-r^2)) .* sqrt(mu.*rho./(E_r.*rho_r))));
	w2=(1./(l.*alpha_r)).*(2*pi-atan(L^2./(S.*sqrt(1-r^2)) .* sqrt(mu.*rho./(E_r.*rho_r))));

	%% search in 4 segments 0->w1, (w1+w2)/2->w1, (w1+w2)/2->w2, w2 and up.
	K0=0.01e3;
	KM=5e3;
	dK=0.005e3;
	w12=(w1+w2)/2;
	Kw12=w12/CR;
	Kw1=w1/Ct;
	Kw2=w2/Ct;
	K1=[K0:dK:KM];
	%K2=[Kw12:-dK:Kw1];
	%K3=[(Kw12+dK):dK:KM];
	%K4=[KM:-dK:(Kw2+dK)];

	%% now for each segement find the solution using a seed guess and pass on to the next solution
	%% BLUE line
	i=1; omega_initial=K1(1)*CR;
	for k=K1
		omega=fminsearch(@(omega) abs(disp_fun(k,omega,rho,lambda,mu,L,rho_r,lambda_r,mu_r,l,S)),omega_initial);
		omega_initial=omega; omega1(i)=omega; i=i+1;
	end

	CP1=omega1./K1; %CP2=omega2./K2; CP3=omega3./K3;
	ohm=[min(omega1)];f=ohm./2./pi;
	plot([0,max(ohm)]./2/pi,[Ct,Ct],'r:',[0,max(ohm)]./2/pi,[CR,CR],'b:',[w1,w1]./2/pi,[0,Ct*1.1],'k:'); hold on
	plot(omega1./2/pi,CP1,'r-')%,omega2./2/pi,CP2,'b-',omega3./2/pi,CP3,'b-');
	xlabel('Frequency /Hz'); ylabel('Velocity /ms^-^1'); axis tight
	title('Velocity against frequency for changing resonator length')
	xlim([0,1000e3])
end

Unrecognized function or variable 'disp_fun'.

Error in solution (line 62)
omega=fminsearch(@(omega) abs(disp_fun(k,omega,rho,lambda,mu,L,rho_r,lambda_r,mu_r,l,S)),omega_initial);

Error in fminsearch (line 201)
fv(:,1) = funfcn(x,varargin{:});

Answer 1

[Star Strider]

The code is incomplete and cannot run as posted.

Using the .fig file instead:

F = openfig('Velocity against frequency for changing resonator length.fig');

Ax = gca(F);

Lm = findobj(Ax, 'Type','line');

Xq = 5E+5;

for k = 1:numel(Lm)

Xv{k,:} = Lm(k).XData;

Yv{k,:} = Lm(k).YData;

Zv{k,:} = Lm(k).ZData;

if numel(unique(Xv{k})) > 1

Yq(k,:) = interp1(Xv{k},Yv{k}, Xq)

else

Yq(k,:) = NaN;

end

end

figure

plot(1:numel(Yq), Yq, 'x')

grid

xlabel('Arbitrary Vector')

ylabel('Velocity')

produces:

Here, ‘Xq’ is the desired frequency of Hz and ‘Yq’ are the interpolated values that intercept that value. Since ‘Resonator Length’ is nowhere defined in the code, I plotted it against the index vectors of ‘Yq’. If ‘ResonatorLength’ is defined, it should be assigned within the if block under both conditions, so that it can be plotted as the independent variable in the figure plotted in my code, for example:

if numel(unique(Xv{k})) > 1

RL(k,:) = "Resonator Length At This Value Of The Existing Data";

Yq(k,:) = interp1(Xv{k},Yv{k}, Xq)

else

RL(k,:) = "Resonator Length At This Value Of The Existing Data";

Yq(k,:) = NaN;

end

and then plot ‘Yq’ against ‘RL’ instead of against ‘Arbitrary Vector’.

.

[aman verma]

Thank you so much for your help so far, its really appreciated.

The resonator length is defined by the use of linspace where l is the length of the resonator. How can this linspace be put into RL and thus produce the appropriate plot? (the attached image is an example of what the plot is to look like.

for x=linspace(0.001,0.01,100)
    l=x;

[Star Strider]

I cannot run the code, so I cannot figure out how ‘x’ is used in it, or with respect to the plot. There does not appear to me to be any specific relation between ‘x’ (or ‘l’) and whatever is being plotted.

So, I am going with this option:

RL = linspace(0.001,0.01,numel(Yq));

figure

plot(RL, Yq, 'x')

grid

xlabel('Resonator Length')

ylabel('Velocity')

producing this plot:

That is the best I can do.

.