I am creating a user define function that calculates a polynomial using the bisection method. I am getting parse error near line 14 of the file.

function [fBis, nBis] = practice1 (y, fa, fb, eps);

nBis = 0;

x = 0;

While (x < eps)

    x1 = y(fa);
    x2 = y(fb);
    fmid = (fa+fb)/2;
    xmid = y(fmid);
    x = abs((fmid-fa)/fmid); 
    If (x1 * xmid < 0)
      fa = fa;
      fb = fmid;
    else
      fa = fmid;
      fb = fb;
    end
  nBis = nBis + 1;
  end

fBis = fmid;

end

[madhan ravi]

y, fa, fb, eps values?

[Jamilah Carlos]

They are given in a separate m-file.

y=@(f) 1./sqrt(f) + 2.0*log10((rough/d)/3.7 + 2.51./(Re.*sqrt(f)));

dens = 999; visc = 1.12e-3; d = 0.25; v = 10; rough = 0.05e-3;

fa = 0.008; fb = 0.1; eps = 0.0001;

[Jamilah Carlos]

I forgot to add in that Re was already in the other file:

Re = dens*v*d/visc

It was included in the separate m-file with all the variables. My only problem is that there is a parse error whenever I try to end my while loop. It says syntax error. I'm not sure where it is coming from.

[Kevin Chng]

Do you mind post the error here? So we could understand it better.

[madhan ravi]

Instead of giving your codes bit by bit why not post the whole code ? It could save a lot of time!!

[Jamilah Carlos]

I did not know it was necessary to post the other m-file since I was just creating a user-defined function that was going to be called on. It is a meant to be a general function that could solve any polynomial.

The error just says this:

parse error near line 16 of file /Users/Jami/Documents/School Work/Course Documents/Fall 2018 /ME 232A CAP Engineering Computations /Assignments/Files/practice1.m

syntax error

>>> else

[Kevin Chng]

I guess some data files or m.files are not called properly.

Try the way mentioned by Image Analyst in the link below. https://www.mathworks.com/matlabcentral/answers/140438-what-does-parse-error-basically-mean

I'm not sure what is your line16 of the undermentioned m.file.

[Jamilah Carlos]

line 16 is: else

[Kevin Chng]

Bit weird on this. Do you mind copy my code in the answer, and paste it in the new script, and try to run it.

See what is the result. Put

clear all; clc;

at the beginning of the second script.

[madhan ravi]

Try elseif (x1 * xmid > 0)

Answer 1

[Kevin Chng]

Hi Jamilah Carlos,

y=@(f,rough,d, Re) 1./sqrt(f) + 2.0*log10((rough/d)/3.7 + 2.51./(Re.*sqrt(f)));

There are many unknown variables in your equation - rough, d, Re.

In your another script, there are rough and d variable. However, I did't see the Re.

To solve your question, you must assign those variables to your equation. Refer to my code,

function [fBis, nBis] = practice1 (y, fa, fb, eps, d, rough, Re)
nBis = 0;
x = 0;

while (x < eps)
x1 = y(fa, rough, d, Re);
x2 = y(fb, rough, d, Re);
fmid = (fa+fb)/2;
xmid = y(fmid, rough, d, Re);
x = abs((fmid-fa)/fmid); 
if (x1 * xmid < 0)
  fa = fa;
  fb = fmid;
else
  fa = fmid;
  fb = fb;
end

nBis = nBis + 1;
end
fBis = fmid;

end

In your second script,

y=@(f,rough,d, Re) 1./sqrt(f) + 2.0*log10((rough/d)/3.7 + 2.51./(Re.*sqrt(f)));
dens = 999; visc = 1.12e-3; d = 0.25; v = 10; rough = 0.05e-3;
fa = 0.008; fb = 0.1; eps = 0.0001; Re= 0.2;
[fBis, nBis] = practice1 (y, fa, fb, eps, d, rough, Re)

You have to change the value of Re, i simply assign 0.2 to it.

Please accept my answer if it is working for your case.

[madhan ravi]

+1 @ Kevin nice.