Why am I receiving Not enough input arguments?

hello, I am working on an assignment where I need to find the pressure difference for 9 different states. Everything goes fine until i reach the turbulent flow section, where I can not figure out what to do. Any help would be appreciated. I have posted the three codes and the error towards the bottom

% P1 driver
clear
clc

p = 680;
u = 2.92*10^-4;
d = .01;
L = 2;



M = zeros(3,3);

% V1 E1
e = 0;
V = 0.05;
[f,flow, P] = fandp(V, d, L, e, p, u);
P1 = P;
M(1,1) = P1;

% V1 E2
e = 0.00015;
V = 0.05;
[f,flow, P] = fandp(V, d, L, e, p, u);
P2 = P;
M(1,2) = P2;

% V1 E3
e = 0.002;
V = 0.05;
[f,flow, P] = fandp(V, d, L, e, p, u);
P3 = P;
M(1,3) = P3;

% V2 E1
e = 0;
V = 0.1;
[f,flow, P] = fandp(V, d, L, e, p, u);
M(2,1) = P;

% V2 E2
e = 0.00015;
V = 0.1;
[f,flow, P] = fandp(V, d, L, e, p, u);
M(2,2) = P;

% V2 E3
e = 0.002;
V = 0.1;
[f,flow, P] = fandp(V, d, L, e, p, u);
M(2,3) = P;

% V3 E1
e = 0;
V = 0.5;
[f,flow, P] = fandp(V, d, L, e, p, u);
M(3,1) = P;

% V3 E2
e = 0.00015;
V = 0.5;
[f,flow, P] = fandp(V, d, L, e, p, u);
M(3,2) = P;

% V3 E3
e = 0.002;
V = 0.5;
[f,flow, P] = fandp(V, d, L, e, p, u);
M(3,3) = P;

here is the called function fandp:

function [f,flow, P] = fandp(V, d, L, e, p, u)
%flow_type Determines if flow is laminar, in transition, or turbulent
%   V = velocity (m/s)
%   d = diameter of pipe (m)
%   L = length of pipe (m)
%   e = roughness of pipe (m)
%   p = density of fluid (kg/m^3)
%   u = dynamic viscosity of fluid (Pa*s)
%   flow = laminar, transition, or turbulent
%   pressure = pressure difference required for desired flow

Re = 0;
P = 0;

%setup variables
    xMin= -0.3;
    xMax= 0.3;
    tol=10^-8;

% gravity
g = 9.81;

%Calculate Reynolds Number
Re = (p*V*d)/u;


%Determine Flow Type
if Re < 2000
    flow = 'laminar';
elseif Re > 3000
    flow = 'turbulent';
elseif Re > 2000 && Re < 3000
    flow = 'transition';
end

% f
if strcmp(flow, 'laminar')
    f = (64/Re);
elseif strcmp(flow, 'turbulent')
    [x_r] = bisect(@func,xMin,xMax,tol);
    f = x_r;
elseif strcmp(flow, 'transition')
    f = NaN;
end

check = isnan(f);

if check == 1
    P = NaN;
else
    % h
    h = f*(L/d)*((V^2)/(2*g));
    % P
    P = p*g*h;
end
end


% Testing Function 
function [f]=func(x,e,d,p,V,u)
f = -2*log((e/d)/3.7+(2.51/(p*V*d/u)*x^(1/2)))-(1/x^(1/2));
end

and here is the bisection function:

function [x_r,err,iter] = bisect(func,xMin,xMax,tol)
%This program will use the bisection method to find the roots to 
%a function
%INPUTS:
%func is the function you want to find roots to
%xMin is the low range to begin the search
%xMax is the high value to search within
%tol is the acceptable error. The smaller the tol, the more
%iterations required. Recommended value is 1e-8 
%OUTPUTS:
%x_r is the root to func
%err is the relative error of x_r, as measured by X-tol
a=func(xMin);
b=func(xMax);
 
if a*b>0
    disp('Error: ends must evaluate to opposite signs');
    return
end
 
iter=0;
x_Last=xMin;
err=abs(xMax-xMin);

iters = [];
roots = [];
errs =[];
 
while err>tol && iter<50
        iter=iter+1;
        iters = [iters,iter];
    	x_r =(xMax+xMin)/2; 
        c=func(x_r);
        if a*c>0
            xMin=x_r;
            a=c;
        elseif a*c<0
            xMax=x_r;
            b=c;
        else
            return;
        end
    
        if abs(x_r)>1
            err=abs((x_r-x_Last)/x_r);
        else 
            err=abs(x_r-x_Last);
        end
        x_Last=x_r; 
        roots =[roots,x_r];
        errs =[errs,err];
end

%this renames the arrays to the name they are supposed
%to be according to the Lab03 .docx
x_r = roots;
err = errs;
iter = iters;
end

here is the error i am getting:

Not enough input arguments.

Error in fandp>func (line 61)
f = -2*log((e/d)/3.7+(2.51/(p*V*d/u)*x^(1/2)))-(1/x^(1/2));

Error in bisect (line 13)
a=func(xMin);

Error in fandp (line 40)
    [x_r] = bisect(@func,xMin,xMax,tol);

Error in P1driver (line 56)
[f,flow, P] = fandp(V, d, L, e, p, u);

Can someone please tell me where I went wrong?

Answer 1

[James Tursa]

The error seems pretty clear, you are calling func( ) without enough input arguments. The func( ) signature has six inputs:

function [f]=func(x,e,d,p,V,u)

and here you are calling it with less than six inputs:

a=func(xMin);
b=func(xMax);
    :
c=func(x_r);

Instead of passing @func to bisect( ) maybe pass this instead:

@(x)func(x,e,d,p,V,u)

[Andrew Hannah]

Thank you! I got it working based on your suggestion.

Answer 2

[Matt Butts]

I am pretty sure this is because you have defined func as having 6 inputs, but when you call it from within bisect you are only passing one input.