How to pass multiple arguments to a function stored in a vector?

Hello guys;

I'm making a program for my college assignment and I got stuck in a situation. So, I have a vector X storing x1,x2,x3....xn (i.e. X = [x1,x2,x3,...xn] ) and a function f(x1,x2,x3,...xn). e.g. let f(x1,x2) = sin(x1)+cos(x2) and X = [1,2]. So I want to write a code which accepts the values stored in X (i.e. x1 and x2 in this given example) and use them for function arguments (i.e. f(x1,x2) = f(1,2) = sin(1)+cos(2)).

[KALYAN ACHARJYA]

X=[......]

Pass the entire vector

function out_put_arguments=fun1(X)
.........
end 

If I don't understand the question, pleas can you provide more with the sample example.

[abhisek singh]

Yeah I think you didn't understand the question. So, let me explain it with an example. So, let's say we asked user to give us the number of equations he want to input ( i.e. N and N >=1) and let user enters N = 3; so by that means user will enter 3 equations containing 3 variables (x1,x2,x3). We'll take input using this code.

clc;
N = input("Enter the number of equations : ");
Xns = strjoin(compose('x%d', 1:N), ',');
F = cell(N,1);
for i = 1:N
    func_str = input("Write function f(x1,x2,...xn): ",'s');
    F{i} = str2func(sprintf('@(%s) %s', Xns, func_str));
end

And let these are the inputs we have from user. In this case F cell will contain 3 equations.

and Xns = 'x1,x2,x3'.

Now we'll ask user for values of x1,x2 and x3 that are being used in equations for calculations and we're storing the

inputs (i.e. the value of x1,x2, and x3 in a vector Xs) using following code.

Xs = [];
for i = 1:N
    Xs(i) = input("Enter the value of respective variables: ");
end

Now we have a cell F storing equations (with variables x1,x2 and x3) and a vector Xs storing the values of x1,x2 and x3. So if I want to get the value of any eqaution with the values of x1,x2 and x3, I can write F{1}(x1,x2,x3) [and I'll get the value of equation stored in F{1}] but the problem is user can give any number of equations and variables which is unkown and hence I can't say F{1}(x1,x2,x3) every time because may be user have given N = 5, i.e. 5 variables ( i.e. x1,x2,x3,x4,x5) and hence this is becoming a problem for me to solve. So Is there any way to pass values of x1,x2,x3...xn stored in Xs in F{i} to get the value of equation stored? I hope you got the question I'm stuck with.

Answer 1

[Stephen23]

The solution is to use a cell array for the input values, for example:

C = cell(1,N);
for k = 1:N % do NOT use i
    str = input(sprintf('Enter variable x%d: ',k),'s');
    C{k} = str2double(str);
end

and then when calling any function, use a comma-separated list, e.g. with the first function:

F{1}(C{:})

You could even call all functions using cellfun:

cellfun(@(f)f(C{:}),F)

Read more about comma-separated lists:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

[abhisek singh]

thanks and your like a god for me.

works perfectly. one more thing please recommend me some sources to learn more in MATLAB, I have just started it ( on 25-11-2020) :)

[Stephen23]

https://www.mathworks.com/learn/tutorials/matlab-onramp.html

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

https://www.mathworks.com/matlabcentral/answers/228557-experts-of-matlab-how-did-you-learn-any-advice-for-beginner-intermediate-users