Keep getting error with sample code

So the commented up code was the one that was provided to essentially plot my part, yet I keep getting these errors: Undefined function 'number_of_solutions' for input arguments of type'double'.

Error in Lab4 (line 68)

n = number_of_solutions(A(m), b(m));

Not sure why I'm getting these errors, are there any toolboxes or something that I'm missing. Thanks.

clear, clc, close all
syms m f
A = @(m) [m -1; (3*m-m^3) (1-3*m^2)];
b = @(m) 2*(1-m) * [1; (m^2+4*m +1)];
det(A(m));
f = matlabFunction(det(A(m)));
eqn = f(m) == 0;
solve(eqn)error wit

dx = 0.05; dy = 0.25;
for m = -2.6 : 0.2 : 2.6
 n = number_of_solutions(A(m), b(m));
 if f(m) == 0
 zero_marker = plot(m, 0, 'bo', 'MarkerSize', 16, 'MarkerFaceColor', 'white');
 else
 plot(m, f(m), 'bh', 'MarkerSize', 10, 'MarkerFaceColor', 'green')
 end
 the_text = text(m+dx, f(m) + dy, num2str(n), 'FontSize', 24) ;
 the_text.set('FontWeight', 'bold', 'HorizontalAlignment', 'center', 'VerticalAlignment', 'bottom');
 % Auto Color Code the Zero Markers and the Text
 if n==0 % inconsistent! No solutions
 the_text.set('Color', 'red')
 % Add code to set the MarkerFaceColor for zero_marker to red.
 set(zero_marker, {'MarkerFaceColor'}, get(zero_marker, 'red'));

 elseif n==inf % there are free variables
 the_text.set('string', '\infty')
 % Add code to set the MarkerFaceColor for zero_marker to yellow.
 set(zero_marker, {'MarkerFaceColor'}, get(zero_marker, 'Yellow'));
 else
 the_text.set('Color', 'green') % unique solution!
 end
end

Answer 1

[Cris LaPierre]

Where was this coded up? It looks like a homework assignment from Drexel University (Engr 231).

The issue is that number_of_solutions is not a matlab function, and your code does not create it either. The result is an error because MATLAB can't find it. Perhaps you were provided with additional code you are overlooking?

A = number_of_solutions(4,5)

Unrecognized function or variable 'number_of_solutions'.

[Stanley Zhu]

Yes it's a lab assignment from Drexel, I forgot to add in that I did also create a new function file and pasted this code in as instructed. I'm not certain what I'm getting wrong as it's still the same issue.

function [number] = number_of_solutions(A,b)
    % Input A is an mxn matrix. b is a mx1 column vector. 
    % The unknown x is an nx1 column vector.  
    % Finds the number of solutions of the linear system Ax = b
    % Number of solutions can only be 
    %   0. zero, (inconsistent) 
    %   1. one (unique) or
    % inf. infinite (there are free variables). 
    %      (Infinity in MATLAB is written inf or Inf.)

    number_of_variables = numel( A(1,:)); % x1, x2, ..., xn
    AM = [A b]; % augmented matrix
    if rank(AM) > rank(A) % system is inconsistent. There is a pivot in the final column.
        number = 0;
    elseif rank(A) < number_of_variables
        number = inf;   % There are free variables
    else  
        number = 1; % unique!
    end  
end

[Stanley Zhu]

Ok nevermind it seems I goofed up in terms of where I created the function folder, should've definitely had some rest cause I completely skipped over the line. Thanks.