find the variance of all elements in an array in rust

To find the variance of all elements in an array in Rust, you can follow these steps:

1. Find the mean of the elements in the array.
2. For each element in the array, subtract the mean and square the result.
3. Sum up all the squared differences.
4. Divide the sum by the number of elements in the array minus one to get the variance.

Here's how you can implement this in Rust:

main.rs
fn find_variance(arr: &[f64]) -> Option<f64> {
    let n = arr.len() as f64;
    if n <= 1.0 {
        return None;
    }
    let mean = arr.iter().sum::<f64>() / n;
    let variance = arr.iter().map(|x| (x - mean).powi(2)).sum::<f64>() / (n - 1.0);
    Some(variance)
}
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This function takes an array of f64 elements and returns an Option<f64> which is Some(variance) if the array has more than one element, or None otherwise. The mean of the elements is calculated using the sum method of the iterator returned by the iter method on the array. The squared differences are calculated using the map method of the iterator, and then summed up using the sum method. The variance is then calculated by dividing the sum by n - 1.0 and returned as an Option<f64>.