Bisection help PLS HELP ME

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Triggs
Triggs on 19 Jul 2019
Edited: Triggs on 19 Aug 2019
I have this code for a bisection method but I cant seem to figure out why it wont work I just get this error
every thing else is given
any help is appreciated thanks
Error using *
Incorrect dimensions for matrix multiplication. Check that the
number of columns in the first matrix matches the number of rows in
the second matrix. To perform elementwise multiplication, use '.*'.
Error in bisectiona>f (line 65)
x=(2*Fo/wn.^2-w.^2)*sin((wn-w/2)*t)*sin((wn+w/2)*t);
Error in bisectiona (line 14)
f_left = f(x_left);
function bisectiona
% Bisection method: Used for solving an equation, and finding an
% approximate solution to an equation.
clc
% The number of bisection steps
n = 32;
% define the initial interval
a = 41;
b = 69;
fprintf('\n initial interval [%g, %g] \n total bisection steps %d\n', a,b,n);
% Check that a root does exist in the chosen interval
x_left = a;
x_right = b;
f_left = f(x_left);
f_right = f(x_right);
if f_left*f_right > 0
end
% Bisection: The method
for i=1:n
if f_left == 0
% The exact root of the equation is found at the lower bound
% of the chosen interval
fprintf('\n stage %g root %g with zero absolute error \n',i,x_left);
return;
end
if f_right==0
% The exact root of the equation is found at the upper bound
% of the chosen interval
fprintf('\n stage %g root %g with zero absolute error \n',i,x_right);
return
end
% Bisection method: The process
x_mid = (x_left+x_right)/2.0;
f_mid = f(x_mid);
if f_left*f_mid <= 0
% There is a root in [x_left,x_mid]
x_right = x_mid;
f_right = f_mid;
end
if f_left*f_mid > 0
% There is a root in [x_mid,x_right]
x_left = x_mid;
f_left = f_mid;
end
% Calculate the approximate root for current step
root = (x_left+x_right)/2.0;
% Calculate the absolute error for current step
abs_err=(x_right-x_left)/2.0;
fprintf('\n stage %g root %g absolute error < %g \n',i,root,abs_err);
end
%check satisfaction of equation at end of process
residual = f(root);
fprintf('\n final residual = %g \n',residual);
end
%Created Subfunction to define equation f(x)
function f_value = f(~)
k = 2800;
m = 0.6705;
Fo = 2.0535;
t = 9.177;
x = 0.0253;
w = 77:0.1:80;
wn= sqrt(k/m);
fo= Fo/m;
x=(2*Fo/wn.^2-w.^2)*sin((wn-w/2)*t)*sin((wn+w/2)*t);
f_value = x;
end

Accepted Answer

KALYAN ACHARJYA
KALYAN ACHARJYA on 19 Jul 2019
Edited: KALYAN ACHARJYA on 19 Jul 2019
"but I cant seem to figure out why it wont work I just get this error"
function f_value=f(~)
k = 2800;
m = 0.6705;
Fo = 2.0535;
t = 9.177;
x = 0.0253;
w = 77:0.1:80;
wn= sqrt(k/m);
fo= Fo/m;
x=(2*Fo/wn^2-w.^2).*sin((wn-w./2)*t).*sin((wn+w./2).*t);
f_value = x;
end
Main Script:
clc
clear all;
close all;
% approximate solution to an equation.
% The number of bisection steps
n = 32;
% define the initial interval
a = 41;
b = 69;
fprintf('\n initial interval [%g, %g] \n total bisection steps %d\n', a,b,n);
% Check that a root does exist in the chosen interval
x_left = a;
x_right = b;
f_left=f(x_left);
f_right=f(x_right);
if (f_left.*f_right)> 0
end
% Bisection: The method
for i=1:n
if f_left == 0
% The exact root of the equation is found at the lower bound
% of the chosen interval
fprintf('\n stage %g root %g with zero absolute error \n',i,x_left);
return;
end
if f_right==0
% The exact root of the equation is found at the upper bound
% of the chosen interval
fprintf('\n stage %g root %g with zero absolute error \n',i,x_right);
return
end
% Bisection method: The process
x_mid = (x_left+x_right)/2.0;
f_mid = f(x_mid);
if f_left.*f_mid <= 0
% There is a root in [x_left,x_mid]
x_right = x_mid;
f_right = f_mid;
end
if f_left.*f_mid > 0
% There is a root in [x_mid,x_right]
x_left = x_mid;
f_left = f_mid;
end
% Calculate the approximate root for current step
root = (x_left+x_right)/2.0;
% Calculate the absolute error for current step
abs_err=(x_right-x_left)/2.0;
fprintf('\n stage %g root %g absolute error < %g \n',i,root,abs_err);
end
%check satisfaction of equation at end of process
residual = f(root);
fprintf('\n final residual = %g \n',residual);
Command Window:
pic22.png
Please note: I removed the code errors only.
  1 Comment
madhan ravi
madhan ravi on 19 Jul 2019
There are some unnecessary lines of code.

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