why is my ea not being recognized?

 clc; clear all;

L = 1.25; E = 50000; I = 30000; w0 = 2.5;
syms x
f(x) = (w0/(120*E*I*L))*(-x^5+2*(L^2)*(x^3)-(L^4)*x);
df = diff(f,x); 
true = df(2); 
roots = solve(f==0, x);
true_roots = double(roots);
xl = 200;
xu = 300;
xr = (xl + xu) / 2;
es = 0.001;
xr_new(1) = xr;
if f(xl) * f(xu) < 0
    disp('The function changes sign within this bound')
    for i = 1:100
        val(i) = f(xl) * f(xr_new(i));
        if val(i) < 0
            disp('The root lies in the lower interval')
            xu = xr_new(i);
        elseif val(i) > 0
            disp('The root lies in the upper interval')
            xl = xr_new(i);
        else val = 0;
            fprintf('The approximate root of the function is %1.2f \n',xr_new(i))
            break
        end
        xr_new(i+1) = (xl + xu) / 2;
        ea = abs((xr_new(i+1) - xr_new(i))./xr_new(i+1));
        if ea < es
            break
        end
    end
else
    disp('The function does not change sign within this bound')
end

The function does not change sign within this bound

% Print the results
ea = ea*100;

Unrecognized function or variable 'ea'.

fprintf('The absolute approximate error is: %1.5f \n',ea)
n_iterations = i+1;
fprintf('The total number of iterations are: %d \n',n_iterations)
root = xr_new(1,end);
fprintf('The approximate root of the function is: %1.5f \n', root)
x1 = -1000 : 1000;
y1 = f(x1);
y = double(y1);
xmin = -1000; xmax = 1000; ymin = -0.5; ymax = 0.5;
plot(x1, y1)
hold on
plot(true_root,0,'mo','MarkerFaceColor','m')
set(gca,'XAxisLocation','origin','YAxisLocation','origin','XMinorTick','on')
xlabel('x \rightarrow')
ylabel('\uparrow f(x)')
title('Graphical root')

  NOTE:-

Matlabsolutions.com provide latest MatLab Homework Help,MatLab Assignment Help , Finance Assignment Help for students, engineers and researchers in Multiple Branches like ECE, EEE, CSE, Mechanical, Civil with 100% output.Matlab Code for B.E, B.Tech,M.E,M.Tech, Ph.D. Scholars with 100% privacy guaranteed. Get MATLAB projects with source code for your learning and research.

There are a few inconsistencies.

 

(1) The simulation in [for ... end] loop never reached due to if condition f(xl)*f(xu) <0. The actual values of f(xl)*f(xu) were in sym and greater than 0. Therefore, by changing it to double and the if condition (f(xl)*f(xu)>), you will get the simulation results.

 

(2) The found true roots were in sym.

 

(3) Similarly, y1 = f(x1) was in sym that need to be numerical. Thus, double() is needed.

 

(4) if val = 0 is not correct that must be val == 0.

 

(5) It is better (must be) to use fplot() instead of plot to plot actual faction. By this way tru solutions can be shown explicitly - see figure (2).

 

Here is the corrected code:

 

 

clc; clearvars;
L = 1.25; E = 50000; I = 30000; w0 = 2.5;
syms f(x)
f(x) = (w0/(120*E*I*L))*(-x^5+2*(L^2)*(x^3)-(L^4)*x);
df = diff(f,x); 
true = double(df(2)); 
roots = vpasolve(f==0, x);
true_roots =double(roots(:));
xl = 200;
xu = 300;
xr = (xl + xu) / 2;
es = 0.001;
xr_new(1) = xr;
if double(f(xl)) * double(f(xu)) >0
    disp('The function changes sign within this bound')
    for i = 1:100
        val(i) = double(f(xl)) * double(f(xr_new(i)));
        if val(i) < 0
            disp('The root lies in the lower interval')
            xu = xr_new(i);
        elseif val(i) > 0
            disp('The root lies in the upper interval')
            xl = xr_new(i);
        else val == 0;
            fprintf('The approximate root of the function is %1.2f \n',xr_new(i))
            break
        end

SEE COMPLETE ANSWER CLICK THE LINK

https://www.matlabsolutions.com/resources/why-is-my-ea-not-being-recognized-.php