How do I find a variable number of functions?

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Volkan
Volkan 2014-10-15
评论： Star Strider 2014-10-15
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.
  2 个评论
the cyclist
the cyclist 2014-10-15
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
Volkan 2014-10-15
编辑：the cyclist 2014-10-15
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]

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采纳的回答

Star Strider
Star Strider 2014-10-15
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.

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