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Error using stem (line 43) X must be same length as Y

I am trying to error of bisection method using matlab with stem the error is calculated for each iteration by abs(x2-x1), so I need to draw it using stem the output must be something like that: enter image description here

this is my code:

close all; clear ; clc; 
 syms x;
 
 f=@(x)(x^(2))-(2);
 x1=1;
 x2=2;
 acc=10^(-8);
 n=0;
 
 
 
 disp ('            Bisection Method')
 disp ('===========================================')
 disp ('iteration     root(P-hat)            error')

 
 while (abs(x2-x1)>acc)
     n = n + 1; 
     xm=(x1+(x2-x1)/2); 
     if (f(x1)*f(xm)<0)
         x2=xm;
     else
         x1=xm;
     end
     figure(1)
     X = linspace(0,30);
     Y = abs(x2-x1);
     stem(X,Y);
     grid on
     hold on
     
     fprintf('%3d %20.8f %20.10f \n', n, xm, abs(x2-x1));
 end

and this error is showing for me:

            Bisection Method
===========================================
iteration     root(P-hat)            error
Error using stem (line 43)
X must be same length as Y.

Error in Ass1Bisection (line 28)
     stem(X,Y);

as you can seen, the values of the iterations, root, and error that not printed even because of this error

how may I solve it?

Solution

  • In this case Y is created empty and the instruction Y(end+1) will make it to add one element.

    close all; clear ; clc; 
 syms x;
 
 f=@(x)(x^(2))-(2);
 x1=1;
 x2=2;
 acc=10^(-8);
 n=0;
 
 
 
 disp ('            Bisection Method')
 disp ('===========================================')
 disp ('iteration     root(P-hat)            error')

 Y = []
 while (abs(x2-x1)>acc)
     n = n + 1; 
     xm=(x1+(x2-x1)/2); 
     if (f(x1)*f(xm)<0)
         x2=xm;
     else
         x1=xm;
     end
     figure(1)
     Y(end+1) = abs(x2-x1);
     stem(1:length(Y),Y);
     grid on
     hold on
     
     fprintf('%3d %20.8f %20.10f \n', n, xm, abs(x2-x1));
 end