vertcat error! in fsolve for 3 variables

I am trying to optimse a set of 3 quadratic equations with 3 varaibles..

function Wheel_align = myfunct(C)
K1 = 5;
K2 =5;
theta1 = pi/3;
x1=0;
x2=5;
y1=0;
y2=0;
z1=0;
z2=0;

Wheel_align = [(x1 - C(1))^2 + (y1 - 4.33)^2 +(z1- C(2))^2 - (K1)^2;
 (x2 - C(1))^2 + (y2 - 4.33)^2 +(z2 - C(2))^2 - (K1)^2;
 (x1 - C(1))*(x2 - C(1)) + (y1 - 4.33)*(y2 - 4.33)+ (z1 - C(3))*(z2 - C(3))- abs(K1*K2)*cos(theta1);

C0 = [0;-5;0];           % Make a starting guess at the solution
options=optimset('Display','iter');   % Option to display output
[C,fval] = fsolve(@myfunct,C0,options)  % Call solver

ERROR is as follows:

Error using vertcat
CAT arguments dimensions are not consistent.

Error in myfunct (line 21)
Wheel_align = [(x1 - C(1))^2 + (y1 - 4.33)^2 +(z1- C(2))^2 - (K1)^2;

Error in fsolve (line 243)
            fuser = feval(funfcn{3},x,varargin{:});

Error in main_wheel (line 3)
[C,fval] = fsolve(@myfunct,C0,options)  % Call solver
Caused by:
    Failure in initial user-supplied objective function evaluation. FSOLVE cannot
    continue.

Answer 1

[Walter Roberson]

You should have shown us the function header for wheel_align . I will speculate that you define it as having a single parameter named C.

The length of C that is passed in is the same as the length of your starting guess, C0. Your C0 should have at least 6 elements.

[Shobhit@]

Hi here is the function header.

function Wheel_align = myfun(C)

i still can't understand where i am making the mistake

[Shobhit@]

How do i change the length of C and how do i specify the 6 starting guess for the solution for all 6 varaibles

[Shobhit@]

I changed C0 = [ -5;-5;-5;-5;-5;-5]

so that length becomes 6 but i am getting the following error now

"Error using vertcat

CAT arguments dimensions are not consistent."

[Walter Roberson]

By the way, Maple says that there is no solution.

The set can be broken up into two non-intersecting subsets, three equations in C1, C2, C3, and three equations in C4, C5, C6.

Maple thinks the equations in C1, C2, C3 are not consistent.

Unfortunately when I step through it solving the triple manually, I am getting stuck in the back substitutions after solving for the second variable.

[Walter Roberson]

With regard to the vertcat problem, I would have to know which line of code the problem is on. Including the entire block of code would be useful. Please edit it in to the original question, as this is a case where exact spacing can be important.

[Walter Roberson]

Your -(K1)^2 terms are going to be treated as separate elements in the list, because - immediately followed (no space) by an expression is unary minus rather than subtraction. And the +(z1-C(3))^2 are unary plus. Spacing is important! Use a space before and a space after those operators.

[Shobhit@]

same problem persists....... maybe my sample values are wrong let me try with the correct one .....

but what is this vertcat error??

[Shobhit@]

Is the error because two separate values can satisfy my equations .. since they are quadratic??

[Walter Roberson]

fsolve() can only find one solution, so do not worry about that aspect.

Meanwhile,

"With regard to the vertcat problem, I would have to know which line of code the problem is on. Including the entire block of code would be useful. Please edit it in to the original question, as this is a case where exact spacing can be important."

[Walter Roberson]

"And the +(z1-C(3))^2 are unary plus. "