How do I find a variable number of functions?

Hello everyone How do I find a variable number of functions? For example, f = x1 + 2 * x2 two variables and variables [x1 x2] 2 variables f = 2 * x + y ^ 2 + u ^ 3 three variables and variables [x y u] 3 variables Thank you very much, everybody.

[the cyclist]

I am not sure what you mean by "find" here. What is your input? What do you expect your output to be. State it in terms of MATLAB, not just a description. We only know what you tell us. Contrary to popular belief, we cannot read minds.

[Volkan]

I'm looking for a command as I mentioned in the following example.

a=????(x1 + 2 * x2) 
b=?????(x1 + 2 * x2) 
a=2 
b=[x1 x2]  
or
c=????(2 * x + y ^ 2 + u ^ 3) 
d=?????(2 * x + y ^ 2 + u ^ 3) 
c=3 
d=[x y u]

Answer 1

[Star Strider]

Use the symvar function, then the length or size functions.

Using symvar:

f1 = 'x1 + 2 * x2'
f2 = '2 * x + y ^ 2 + u ^ 3'

s1 = symvar(f1)
s2 = symvar(f2)

produces:

s1 = 

      'x1'
      'x2'

s2 = 

      'u'
      'x'
      'y'

That is as good as it gets, though. You have to cast the expressions as strings, and they cannot be function handles. I cannot find any other functions that would do what you want.

[Volkan]

Thank you very much I'm looking for exactly that command.

[Star Strider]

My pleasure!