Getting error while trying to access the data of the following plot.

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syms x
warning off
alpha = -0.1;
sigma = 0.1;
eps = -0.1;
e = 0.2;
a = 2;
lambda = 2;
M = 4;
psi_list = [10, 30, 40, 50, 5, 15, 20, 25];
figure
hold on
for i = 1:numel(psi_list)
psi = psi_list(i);
hbar = @(x) a - a.*x + x;
A1 = eps + alpha^3 + (3 * sigma^2 * alpha);
B1 = @(x) (-3 * lambda * M) * ((hbar(x).^2) + (2 .* hbar(x) .* alpha) + (sigma^2) + (alpha^2));
a1 = @(x) tanh(M .* hbar(x));
b1 = @(x) 1 - ((tanh(M .* hbar(x))).^2);
c1 = (M * alpha) - ((M^3 * A1)/3);
d1 = 2 * (M^2) * (1 + lambda);
C1 = @(x) a1(x) + (b1(x) .* c1);
D1 = @(x) d1 .* ((hbar(x).^3) + (3 .* (hbar(x).^2) .* alpha) + (3 .* hbar(x) .* (alpha)^2) + (3 .* hbar(x) .* (sigma)^2) + eps + (3 * alpha * (sigma^2)) + (alpha^3));
f1 = @(x) B1(x) + (3 * lambda .* C1(x) .* hbar(x)) + (3 * lambda .* C1(x) .* alpha) + (D1(x) .* C1(x));
f2 = @(x) 12 * (M^2) * (1 + lambda) .* C1(x);
f3 = psi * (e^3);
f4 = (1 + lambda) *180 * ((1 - e)^2); % 180 is not given in paper
f5 = 1/(2 + lambda);
F = @(x) ((f5 .* f1(x))./f2(x)) + (f3/f4);
q1 = @(x) hbar(x) ./ (2 .* F(x));
Q1 = integral(q1,0,1);
q2 = @(x) 1./(F(x));
Q2 = integral(q2,0,1);
Q = Q1/Q2;
p1 = @(x) (1./F(x)) .* ((0.5 .* hbar(x)) - Q);
P = @(x) integral(p1,0,x);
fplot(P, [0 1])
end
legend(num2str(psi_list'))
ylim([0 1])
set(gca, 'ytick', 0:0.1:1);
set(gca, 'xtick', 0:0.2:1);
xlabel('x')
ylabel('P(x)')
I have tried to access its data but getting error as .....
Index exceeds the number of array elements. Index must not exceed 0.
using the code
open('example.fig');
h = findobj(gca,'Type','line')
x1=get(h(1),'Xdata') ;
y1=get(h(1),'Ydata') ;
x2=get(h(2),'Xdata') ;
y2=get(h(2),'Ydata') ;
x3=get(h(3),'Xdata') ;
y3=get(h(3),'Ydata') ;
x4=get(h(4),'Xdata') ;
y4=get(h(4),'Ydata') ;
x5=get(h(5),'Xdata') ;
y5=get(h(5),'Ydata') ;
x6=get(h(6),'Xdata') ;
y6=get(h(6),'Ydata') ;
x7=get(h(7),'Xdata') ;
y7=get(h(7),'Ydata') ;
x8=get(h(8),'Xdata') ;
y8=get(h(8),'Ydata') ;

Accepted Answer

KSSV
KSSV on 14 Jul 2022
You are plotting the data using fplot. This will give you the function, which you have used to plot when you try to extract the data from figure. If you insist to extract the data from figure (which is not necessary) you may consider using plot.
syms x
warning off
alpha = -0.1;
sigma = 0.1;
eps = -0.1;
e = 0.2;
a = 2;
lambda = 2;
M = 4;
psi_list = [10, 30, 40, 50, 5, 15, 20, 25];
figure
hold on
for i = 1:numel(psi_list)
psi = psi_list(i);
hbar = @(x) a - a.*x + x;
A1 = eps + alpha^3 + (3 * sigma^2 * alpha);
B1 = @(x) (-3 * lambda * M) * ((hbar(x).^2) + (2 .* hbar(x) .* alpha) + (sigma^2) + (alpha^2));
a1 = @(x) tanh(M .* hbar(x));
b1 = @(x) 1 - ((tanh(M .* hbar(x))).^2);
c1 = (M * alpha) - ((M^3 * A1)/3);
d1 = 2 * (M^2) * (1 + lambda);
C1 = @(x) a1(x) + (b1(x) .* c1);
D1 = @(x) d1 .* ((hbar(x).^3) + (3 .* (hbar(x).^2) .* alpha) + (3 .* hbar(x) .* (alpha)^2) + (3 .* hbar(x) .* (sigma)^2) + eps + (3 * alpha * (sigma^2)) + (alpha^3));
f1 = @(x) B1(x) + (3 * lambda .* C1(x) .* hbar(x)) + (3 * lambda .* C1(x) .* alpha) + (D1(x) .* C1(x));
f2 = @(x) 12 * (M^2) * (1 + lambda) .* C1(x);
f3 = psi * (e^3);
f4 = (1 + lambda) *180 * ((1 - e)^2); % 180 is not given in paper
f5 = 1/(2 + lambda);
F = @(x) ((f5 .* f1(x))./f2(x)) + (f3/f4);
q1 = @(x) hbar(x) ./ (2 .* F(x));
Q1 = integral(q1,0,1);
q2 = @(x) 1./(F(x));
Q2 = integral(q2,0,1);
Q = Q1/Q2;
p1 = @(x) (1./F(x)) .* ((0.5 .* hbar(x)) - Q);
P = @(x) integral(p1,0,x);
xi = linspace(0,1) ;
PP = zeros(size(xi)) ;
for j = 1:length(xi)
PP(j) = P(xi(j)) ;
end
plot(xi,PP)
end
legend(num2str(psi_list'))
ylim([0 1])
set(gca, 'ytick', 0:0.1:1);
set(gca, 'xtick', 0:0.2:1);
xlabel('x')
ylabel('P(x)')
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