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use crate::common::utils;
pub fn mirr(values: &[f64], finance_rate: f64, reinvest_rate: f64) -> f64 {
let values = utils::trim_end_zeros(values);
let negative_cf_pv : f64 = utils::powers(1. + finance_rate, values.len(), true)
.iter()
.zip(values.iter())
.filter(|(_r, &v)| v < 0.)
.map(|(r, v)| *v / *r)
.sum();
let positive_cf_fv : f64 = utils::powers(1. + reinvest_rate, values.len(), true)
.iter()
.zip(values.iter().rev())
.filter(|(_r, &v)| v > 0.)
.map(|(r, v)| v * r)
.sum();
(positive_cf_fv / -negative_cf_pv).powf(1. / (values.len() - 1) as f64) - 1.
}
#[cfg(test)]
mod tests {
use super::*;
use crate::common::PRECISION;
#[test]
fn mirr_works() {
let cf = [-1000., 100., 200., 300., 400., 400., 400.];
let finance_rate = 0.1;
let reinvest_rate = 0.1;
let mirr = mirr(&cf, finance_rate, reinvest_rate);
let ans = 0.138453832579;
assert!(
(mirr - ans).abs() <= PRECISION,
format!(
"ans is {} got {}",
ans,
mirr
)
);
}
#[test]
fn mirr_works_negative_cashflow() {
let cf = [-100_000., 18_000., -50_000., 25_000., 25_000., 225_000.];
let finance_rate = 0.05;
let reinvest_rate = 0.1;
let mirr = mirr(&cf, finance_rate, reinvest_rate);
let ans = 0.16288556821502476;
assert!(
(mirr - ans).abs() <= PRECISION,
format!(
"ans is {} got {}",
ans,
mirr
)
);
}
#[test]
fn mirr_works_no_negative_cashflow() {
let cf = [100_000., 18_000., 50_000., 25_000., 25_000., 225_000.];
let finance_rate = 0.05;
let reinvest_rate = 0.1;
let mirr = mirr(&cf, finance_rate, reinvest_rate);
let ans = f64::INFINITY;
assert!(
mirr.is_infinite(),
format!(
"ans is {} got {}",
ans,
mirr
)
);
}
}