Trying to retrieve and display the initial value of an input

From disp(q), I'm trying to show the interval chosen at the beginning from x0 to x1, the loop makes it so that x0 and x1 get changed, therefore I'm trying to specify a = the initial value of x0, and b = the initial value of x1, but Matlab gives an error:

Error in sekantH (line 3)

x0 = a;

Does anyone have a solution to this problem I'm having?

-------------------------------

function f = sekantH(f,x0,x1)

x0 = a;
x1 = b;

format long; 
tol = 10^-10;
count = 0;

for i = 1:1000
    x = x1-f(x1) * (x1-x0)/(f(x1)-f(x0));
    count = count+1;
    if abs(x1-x)<tol
        break
    end
    
    x0 = x1;
    x1 = x;
    f = x;
    count;
    
    q = ['Number of iterations on the interval', ' [', num2str(a), ',' ,num2str(b), '] is = ', num2str(count), '. And the root is: '];
    disp(q)
    
end

Answer 1

[Dave B]

I think you just flipped it, if you want to set a equal to the initial value of x0, do a=x0

demo(5,10)

a=5 b=10 x0=15 x1=30

function demo(x0,x1)
a = x0;
b = x1;
for i = 1:10
    x0 = x0 + 1;
    x1 = x1 + 2;
end
fprintf('a=%d b=%d x0=%d x1=%d\n',a,b,x0,x1)

end

[Ibrahim Ali]

You were correct, I had just flipped it! Works beautifully now, thank you!