error message contain ::: Error using colebrook (line 2) Not enough input arguments. how i can solve it please?

function F = colebrook(Re,K)
F= (1/(-2*log10((K/3.7)+(2.51/Re*sqrt(F)))))^2;
for i=1:20
    Re=i*10^3;
    K=0.00002;

      colebrook(Re,K)
  end
  end

[Walter Roberson]

You need to pass arguments when you call the function, just like you do inside the for loop.

Answer 1

[Walter Roberson]

colebrook = @(Re,K) (1/(-2*log10((K/3.7)+(2.51/Re*sqrt(F)))))^2;

cb = zeros(1,20);
for i=1:20
    Re=i*10^3;
    K=0.00002;
    cb(i) = colebrook(Re,K);
end
cb

[Moath Maqableh]

if you can run this codes after fixed and screenshoot , please do it for me

[Walter Roberson]

Wait... you have defined F in terms of F ? Is the idea to find the F such that the two sides balance?

[Walter Roberson]

Presuming that the idea is to find the F that balances the equation:

colebrook = @(Re,K) (1/(-2*log10((K/3.7)+(2.51/Re*sqrt(F)))))^2;
cf = @(Re,K,F) (1/(-2*log10((K/3.7)+(2.51/Re*sqrt(F)))))^2 - F;
cb = zeros(1,20);
for i=1:20
    Re=i*10^3;
    K=0.00002;
    cb(i) = fzero(@(F) cf(Re,K,F), [0 1]);
end
cb

cb =
  Columns 1 through 6
        0.0212456669959142        0.0176438993118644        0.0159918090443276        0.0149809406929249        0.0142775420985982        0.0137506154874361
  Columns 7 through 12
        0.0133364599564298        0.0129997383391223        0.0127190013698845        0.0124803457077015        0.0122742958406683        0.0120941332432202
  Columns 13 through 18
        0.0119349390546334        0.0117930153254043        0.0116655193666966        0.0115502240640389        0.0114453557666283          0.01134948165294
  Columns 19 through 20
        0.0112614296189815        0.0111802301156452