function calling in a script

To solve for friction factor I have a function file to solve colebrook equation, function file to solve derivative of colebrook equation, function file to solve newton raphson using colebrook and its derivative and finally I have a script file where I need to calculate friction factors when the flow is laminar (this part is easy) and when the flow is turbulent where I need to call the newton raphson function and display its answer. This is the part where I'm confused and can't work out. Help please.

function [fd,no]=newton(Cfd,CfD,x,tol,mit) %mit-maximum iterations, tol-tolerance
for no=1:mit
    fd=x-Cfd(x)/CfD(x);
    err=abs(fd-x);
    x=fd;
    y=Cfd(x);
    if (err<tol)|(relerr<tol)
        break 
    end
end

D=1;
U=1;
rho=1000;
mu=0.0010518;
e=0.003;
Re=rho*U*D/mu;
if Re<2040
    fd=64/Re;
else 
   %how to call the newton raphson function and display its answer???
end

Answer 1

[madhan ravi]

[fd,no]=newton(Cfd,CfD,x,tol,mit) %function call

[Zivile Dailidonyte]

Thank you for your reply. When I do that I get an error that 'fd' is undefined. See my function file for newton raphson below

function [fd,no]=newton(Cfd,CfD,x,tol,mit) %mit-maximum iterations, tol-tolerance
m=0;
fd=x;
xold=x;

while fd==xold
    m=m+1;
    Cfd=colebrook(fd,Re,e,D);
    CfD=colebrook_deriv(fd,Re,e,D);
fd=xold-Cfd/CfD;
error=abs(fd-xold);
fprintf('%m \t %.3f \t %.3f \t 5.3f \t\t %.3f \n', m-1, Cfd, CfD, fd, xold, error);
xold=x;
if error<tol
    break
end
end
disp(['Root = ' num2str(fd) ' found in ' num2str(m) ' iterations'])
disp(['with tolerance of ' num2str(tol)])

[madhan ravi]

https://www.mathworks.com/examples/matlab/community/35851-newtonraphson_example?s_tid=answers_rc2-2_p5_MLT