Help with Matlab function

hello,

i have to implement a MATLAB function findmanyzeros of the form function p = findmanyzeros(f, a, b, n, which finds zeros in the interval [a, b] using the following strategy:

1. Compute n+1 equidistant points xk , k=0,...,n, between a and b

2. For k = 1,...,n, if f(xk) and f(xk−1) have different signs, compute a zero using findzero

3. The output vector p should contain all the computed zeros

my code is as follows:

function p = findmanyzeros(f, a, b, n, tol)
n=n+1;
for k = 1:n
    if f(xk)*f(xk-1)<0 
        findzero(f);
    end
end
p

my code is wrong and i could really appriciate some help, thanks.

Answer 1

[Jan]

This homework question contains useful instructions already:

"Compute n+1 equidistant points xk , k=0,...,n, between a and b"

You've omitted this step. Use the command linspace() to solve it and assign the output to the variable x.

Then you can use f(x(k)) and f(x(k+1)).

I guess, that calling findzero needs the variable tol. Assign the output of this function to p(k).

[Walter Roberson]

However, the output is only to be the list of zeros, so if you assign to p(k) you need to collapse the list later to remove the places no zero was found.

[Lavorizia Vaughn]

the new code i have is as follows:

function p = findz(f,a,b,n,tol) 
x = linspace(a,b,n+1);
p = [];

for k = 2:length(x)
    if f(x(k)) * f(x(k-1)) > 0
        continue 
    else
        z = findzero(f,x(k-1),x(k),tol);
        p = [p,z];
    end
end
disp(p)
end

i am getting the error Unrecognized function or variable 'findzero'.

[Stephen23]

"Unrecognized function or variable 'findzero'."

FINDZERO is not a MATLAB function. Did you mean FZERO?:

https://www.mathworks.com/help/matlab/ref/fzero.html

[Lavorizia Vaughn]

Yes I had the file findzero named wrong. Thanks for the help.