How to evaluate recursive piecewise symbolic functions?

8 次查看（过去 30 天）

Jon 2019-10-10

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/484635-how-to-evaluate-recursive-piecewise-symbolic-functions

Is it possible to define & evaluate recursive piecewise symbolic functions. As a simple example, here's an attempt at a recursive factorial symbolic function:

syms f(n)
syms fn(n)
f(n)=n
fn(n)=piecewise(n==1,1,n>1,f(n)*fn(n-1))

However, when calling it:

fn(4)

There's no recursion in the evaluation. Although f(n) is evaluated, fn(n-1) isn't:

ans=4 fn(3)

I know in this case I could do fn(n)=factorial(n) to get the correct answer, but this is just a simpler version of the recursive function I'm trying to code. Thanks.