**Info**

This question is closed. Reopen it to edit or answer.

# SCRIPT FILE RUNNING ERROR

1 view (last 30 days)

Show older comments

When I run the script file, a can not receive any command on Matlab either any error. However the program stars and runs smoothly. Please help.

The code was:

%bisection method

f = inline('x.^3-0.165.*x.^2+3.993*10^-4');

x= -5.5:0.1:5.5;

y=f(x);

plot(x,y)

grid %from the plot we can see that we have a root between -1 and 1.5 but the height x can not be negative.

%We know that we have a root between 1 and 2(initial guesses)

a=1;

b=2;

m=(a+b)/2;

while abs(f(m))>1e-8

if f(a)*f(m)>0;

a=m;

else

b=m;

end

m=(a+b)/2;

end

m

##### 0 Comments

### Answers (1)

Weird Rando
on 7 May 2016

Edited: Weird Rando
on 7 May 2016

##### 3 Comments

Weird Rando
on 7 May 2016

Edited: Weird Rando
on 7 May 2016

I look into this and found some mistakes. The initial guesses f(a) and f(b) must have opposite signs. And your if statement changed the wrong variable. I also change your while loop to a for loop because f(m) may have positive and negative values. (https://en.wikipedia.org/wiki/Bisection_method)

%bisection method

%f = inline('x.^3-x-2');

f = inline('x.^3-0.165.*x.^2+3.993*10^-4');

x= -5.5:0.1:5.5;

y=f(x);

plot(x,y)

grid %from the plot we can see that we have a root between -1 and 1.5 but the height x can not be negative.

%We know that we have a root between 1 and 2(initial guesses)

a=-1; %f(a) must be negative

b=2; %f(b) must be positive

m=(a+b)/2;

for i = 1:15

if f(m)<0;

a=m;

else

b=m;

end

m=(a+b)/2;

end

m

f(m)

Weird Rando
on 8 May 2016

Edited: Weird Rando
on 8 May 2016

And here is the while loop

%bisection method

%f = inline('x.^3-x-2');

f = inline('x.^3-0.165.*x.^2+3.993*10^-4');

x= -5.5:0.1:5.5;

y=f(x);

plot(x,y)

grid %from the plot we can see that we have a root between -1 and 1.5 but the height x can not be negative.

%We know that we have a root between 1 and 2(initial guesses)

a=-1; %f(a) must be negative

b=2; %f(b) must be positive

m=(a+b)/2;

while abs(f(m)) > 1*10^-8

if f(m)<0;

a=m;

else

b=m;

end

m=(a+b)/2;

end

m

f(m)

### See Also

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!