use core::fmt::Debug;
use core::ops::AddAssign;
use num_traits::{cast::FromPrimitive, float::Float, identities::One, identities::Zero};
#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Clone, Debug)]
pub struct Stats<T: Float + Zero + One + AddAssign + FromPrimitive + PartialEq + Debug> {
pub min: T,
pub max: T,
pub mean: T,
pub std_dev: T,
#[cfg_attr(feature = "serde", serde(skip))]
pub count: usize,
#[cfg_attr(feature = "serde", serde(skip))]
mean2: T,
}
use core::fmt;
impl<T> fmt::Display for Stats<T>
where
T: fmt::Display + Float + Zero + One + AddAssign + FromPrimitive + PartialEq + Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let precision = f.precision().unwrap_or(2);
write!(f, "(avg: {:.precision$}, std_dev: {:.precision$}, min: {:.precision$}, max: {:.precision$}, count: {})", self.mean, self.std_dev, self.min, self.max, self.count, precision=precision)
}
}
impl<T> Stats<T>
where
T: Float + Zero + One + AddAssign + FromPrimitive + PartialEq + Debug,
{
pub fn new() -> Stats<T> {
Stats {
count: 0,
min: T::zero(),
max: T::zero(),
mean: T::zero(),
std_dev: T::zero(),
mean2: T::zero(),
}
}
pub fn update(&mut self, value: T) {
if value > self.max || self.count == 0 {
self.max = value;
}
if value < self.min || self.count == 0 {
self.min = value;
}
self.count += 1;
let count = T::from_usize(self.count).unwrap();
let delta: T = value - self.mean;
self.mean += delta / count;
let delta2: T = value - self.mean;
self.mean2 += delta * delta2;
if self.count > 1 {
self.std_dev = (self.mean2 / (count - T::one())).sqrt();
}
}
pub fn merge<S: Iterator<Item = Stats<T>>>(stats: S) -> Stats<T> {
let mut merged = Stats::new();
for s in stats {
if s.max > merged.max || merged.count == 0 {
merged.max = s.max;
}
if s.min < merged.min || merged.count == 0 {
merged.min = s.min;
}
let merged_count = T::from_usize(merged.count).unwrap();
let s_count = T::from_usize(s.count).unwrap();
if merged.count > 0 {
merged.mean =
(merged.mean * merged_count + s.mean * s_count) / (merged_count + s_count);
merged.std_dev = (merged.std_dev * merged_count + s.std_dev * s_count)
/ (merged_count + s_count);
merged.count += s.count;
} else {
merged.mean = s.mean;
merged.std_dev = s.std_dev;
merged.count = s.count;
}
}
merged
}
}
#[cfg(test)]
mod tests {
use super::*;
use float_cmp::ApproxEqUlps;
#[test]
fn it_works() {
let mut s: Stats<f32> = Stats::new();
let vals: Vec<f32> = vec![1.0, 2.0, 3.0, 4.0, 5.0];
for v in &vals {
s.update(*v);
}
assert_eq!(s.count, vals.len());
assert_eq!(s.min, 1.0);
assert_eq!(s.max, 5.0);
assert!(s.mean.approx_eq_ulps(&3.0, 2));
assert!(s.std_dev.approx_eq_ulps(&1.5811388, 2));
}
}