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Moments::merge: Calculate binomial iteratively

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This commit is contained in:
Vinzent Steinberg 2018-01-11 19:19:56 +01:00
parent 9f2a8ee44f
commit df099b61da
1 changed files with 4 additions and 3 deletions
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7
src/moments/mod.rs
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@ -2,7 +2,7 @@ use core;
use conv::ApproxFrom; use conv::ApproxFrom;
use num_traits::pow; use num_traits::pow;
use num_integer::{IterBinomial, binomial}; use num_integer::IterBinomial;
use super::{Estimate, Merge}; use super::{Estimate, Merge};
@ -178,14 +178,15 @@ impl Merge for Moments {
let mut coeff_a = 1.; let mut coeff_a = 1.;
let mut coeff_b = 1.; let mut coeff_b = 1.;
let mut coeff_delta = 1.; let mut coeff_delta = 1.;
let mut binom = IterBinomial::new(p);
binom.next().unwrap();
for k in 1..=(p - 2) { for k in 1..=(p - 2) {
coeff_a *= -n_b_over_n; coeff_a *= -n_b_over_n;
coeff_b *= n_a_over_n; coeff_b *= n_a_over_n;
coeff_delta *= delta; coeff_delta *= delta;
result.m[p - 2] += f64::approx_from(binomial(p, k)).unwrap() * result.m[p - 2] += f64::approx_from(binom.next().unwrap()).unwrap() *
coeff_delta * coeff_delta *
(self.m[p - 2 - k] * coeff_a + other.m[p - 2 - k] * coeff_b); (self.m[p - 2 - k] * coeff_a + other.m[p - 2 - k] * coeff_b);
// TODO: use IterBinomial
} }
} }