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use num::Float;
#[inline]
pub fn mean<R, F>(data: &R) -> F where R: AsRef<[F]>, F: Float {
data.as_ref().iter().fold(F::zero(), |a,b| a+*b) / F::from(data.as_ref().len()).unwrap()
}
pub fn std_dev<R, F>(data: &R) -> F where R: AsRef<[F]>, F: Float {
let mean = mean(data);
let sum = data.as_ref()
.iter()
.map(|e| (*e-F::from(mean).unwrap()).powi(2))
.fold(F::zero(), |a,b| a+b);
(sum/F::from(data.as_ref().len()).unwrap()).sqrt()
}
pub fn znorm<R, F>(data: &R) -> Vec<F> where R: AsRef<[F]>, F: Float {
let mean = mean(data);
let std_dev = std_dev(data);
data.as_ref().iter().map(|e| (*e-mean) / std_dev).collect()
}