Hello, how do I remove .copied() from u.iter().copied().mean_arithmetic()?

I am trying to make it so I only have to call iter().mean_arithmetic() or into_iter().mean_arithmetic(), but the problem I'm having right now is when I convert impl<I> Iterator for MeanArithmetic<I> to handle &'a T it wont work for u.into_iter().mean_arithmetic().

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use num::ToPrimitive;

pub struct MeanArithmetic<I> {
    iter: I,
    result: f64,
    n: usize,
}

impl<I> MeanArithmetic<I>
where
    I: Iterator,
{
    pub fn new(iter: I) -> MeanArithmetic<I> {
        MeanArithmetic {
            iter,
            result: 0.0,
            n: 0,
        }
    }
}

impl<I> Iterator for MeanArithmetic<I>
where
    I: Iterator,
    I::Item: ToPrimitive,
{
    type Item = f64;

    #[inline]
    fn next(&mut self) -> Option<Self::Item> {
        let value = self.iter.next()?.to_f64()?;
        self.n  = 1;
        self.result  = (value - self.result) / self.n as f64;
        Some(self.result)
    }
}

pub trait MeanExt: Iterator {
    fn mean_arithmetic(self) -> MeanArithmetic<Self>
    where
        Self: Sized,
    {
        MeanArithmetic::new(self)
    }
}

impl<I: Iterator> MeanExt for I {}

fn main() {
    let u = vec![1, 3];
    for n in u.iter().copied().mean_arithmetic() {
        println!("{}", n);
    }

    for n in u.into_iter().mean_arithmetic() {
        println!("{}", n);
    }
}

​