r2rs-nmath 0.1.1

Statistics programming for Rust based on R's nmath package
Documentation 
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// Translation of nmath's dwilcox
//
// Copyright (C) 2020 neek-sss
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

use strafe_type::{FloatConstraint, Natural64, Real64};

use crate::{
    distribution::wilcox::cwilcox,
    func::{choose, lchoose},
    traits::DPQ,
};

/// The density of the Wilcoxon distribution.
pub fn dwilcox<R: Into<Real64>, N1: Into<Natural64>, N2: Into<Natural64>>(
    x: R,
    m: N1,
    n: N2,
    log: bool,
) -> Real64 {
    let mut x = x.into().unwrap();
    let mut m = m.into().unwrap();
    let mut n = n.into().unwrap();

    let mut d = 0.0;

    m = m.round();
    n = n.round();

    if (x - x.round()).abs() > 1e-7 {
        return f64::d_0(log).into();
    }
    x = x.round();
    if x < 0.0 || x > m * n {
        return f64::d_0(log).into();
    }

    let mm = m;
    let nn = n;
    let xx = x;
    d = if log {
        (cwilcox(xx as i32, mm as usize, nn as usize).ln()) - lchoose(m + n, n).unwrap()
    } else {
        (cwilcox(xx as i32, mm as usize, nn as usize)) / choose(m + n, n).unwrap()
    };
    d.into()
}