MATLAB: Using fzero function to solve a nonlinear function with two inputs

Question

Hi,

My aim is to solve a non-linear equation for alpha with given values of X and al (both ranges of values). But I keep getting errors. Here is the code,

INPUTS:

function [n, m, Z] = setglblch
  n=1   ;
  m=1   ;
  Z=14;
end
function [D, A, R] = geom()
  D = 0.3; %Pipe Diameter (m)
  R = D/2; %Pipe Radius (m)
  A = pi*(R^2); %Cross-sectional Area (m^2)
end
function [X] = setX
  X=linspace(0,100,101) ;
end
function [al] = setal
  al=linspace(0,1,101) ;
end

SOLVING:

function y = equationsch(alpha, X, A, m, n, Z, al)
   beta1 = (1-al).^(-1) ;
   beta2 = al/((1/A)-al) ;
   beta3 = 1/alpha ;
   beta4 = beta1-beta2.*beta3 ;
   beta = beta4.^(-1) ;
      if X == 0
          y = 0;
      else
          y1 = al.^(1-0.5) ; 
          y2 = (1-al).^(0.5*m-1) ;
          y3 = X/Z ;
          y4 = beta.^(1+m) ;
          y5 = alpha.^(1+n) ; 
          y6 = (y4/y5).*y3 ;
          y = y1.*y2-y6 ;         
      end
end

WITH ONE INPUT X:

function [alpha] = getalphach
  [A] = geom();
  [n, m, Z] = setglblch();
  X = setX();
  al = setal();
    alpha = arrayfun( @(x) fzero( @(alpha) equationsch(angle, X, D, A, R, m, n, Z, al), [1E-4, pi-1E-4]), X );
end

I GET ERROR Not enough input arguments.

AND WITH TWO INPUTS X AND al:

function [alpha] = getalphach
  [A] = geom();
  [n, m, Z] = setglblch();
  X = setX();
  al = setal();
    alpha = arrayfun( @(x) fzero( @(alpha) equationsch(angle, X, D, A, R, m, n, Z, al), [1E-4, pi-1E-4]), X, al );
end

I GET ERROR Too many input arguments.

How can this be fixed?

Any help truly appreciated!

Answer 1

You need to change the argument from ‘alpha’ to ‘angle’ in the argument list for ‘equationch’.

With that change, it becomes:

alpha = arrayfun( @(x) fzero( @(angle) equationsch(angle, X, D, A, R, m, n, Z, al), [1E-4, pi-1E-4]), X, al );

I did not run your code, but that should resolve at least that problem.