How can I input equations with multiple variables?

Hello there guys;

I'm working on a problem where user is being asked for number of equations he wants to give to code to solve them. e.g. if user gives us n = 2, then there would be maximum 2 variables and equations. if user gives us n = 3, then would be 3 equations with 3 different variables. I'm facing issues with it and I'm using

F = eval(['@(x1,x2))',input("Write function f(x1,x2,...xn): ",'s')]);

but as we can see, I need to increase numbers of varables manually ( x1, x2 in this line ). But I want to make it much flexible and it can take any number of equations with any numbers of variables ( of course number of equtions would be equal to number of variables.

Answer 1

[Ameer Hamza]

evak is evil: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval don't use it. It is better to use str2func() here. Following shows an example

n = 3;
xns = strjoin(compose('x%d', 1:n), ',');
func_str = input("Write function f(x1,x2,...xn): ",'s');
F = str2func(sprintf('@(%s) %s', xns, func_str));

[abhisek singh]

Thank you very much. This was really helpful but I'm new in MATLAB (Started on 25-11-2020) and I don't have deep knowledge in this. Could you please share links to help me to understand terms (like compose,sprintf etc)? that would be so helpful.

[Ameer Hamza]

You can find information about these functions in the documentation. For example, compose(): https://www.mathworks.com/help/matlab/ref/compose.html. You can type the name of the function in the search bar and see its documentation. Also, consider taking the free course: https://www.mathworks.com/learn/tutorials/matlab-onramp.html