When you define a function you need to specify the input arguments as the names of the variables in which the user's input will be stored in the function. You cannot specify them as expressions.
When you call a function you need to pass in an expression. Specifying an unknown variable name as an input argument will not work.
You also don't want to call your function bvp4c since there's already a function by that name in MATLAB.
y = mytimestwo(1:10) % Calling the function I can pass in an expression
y = mytimestwo(z) % Calling the function I cannot pass in an unknown name
% Defining the function I specify a variable name, in this case theInput
%
% When I called this function as y = mytimestwo(1:10) above MATLAB will
% assign 1:10 to the variable theInput inside that mytimestwo call.
function theOutput = mytimestwo(theInput)
theOutput = 2*theInput;
end
% Were I to define a function like below it would error for the same
% reason your function definition would error
%{
function theOutput = mytimestwo(1:10) % Expressions not allowed here
theOutput = 2*theInput;
end
%}
