Error: File: slopfield.m Line: 1 Column: 30 Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses.

Hi i am working on this code:

function [t,y] = eulode(dxdt,[0,0.4],2,0.1,varargin)

% input:

if nargin<4,error('at least 4 input arguments required'),end

ti = tspan(1);tf = tspan(2);

if ~(tf>ti),error('upper limit must be greater than lower'),end

t = (ti:h:tf)'; n = length(t);

if t(n)<tf

t(n+1) = tf;

n = n+1;

end

y = y0*ones(n,1); %preallocate y to improve efficiency

for i = 1:n-1 %implement Euler's method

y(i+1) = y(i) + dydt(t(i),y(i),varargin{:})*(t(i+1)-t(i));

end

But every time i run it i says "Error: File: slopfield.m Line: 1 Column: 30 Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parentheses."

[Walter Roberson]

Duplicated by https://www.mathworks.com/matlabcentral/answers/510225-error-file-slopfield-m-line-1-column-30-invalid-expression-check-for-missing-multiplication-ope