IronCalc/base/src/functions/statistical/gauss.rs

use statrs::distribution::{ContinuousCDF, Normal};

use crate::expressions::token::Error;
use crate::expressions::types::CellReferenceIndex;
use crate::{calc_result::CalcResult, expressions::parser::Node, model::Model};

impl Model {
    pub(crate) fn fn_gauss(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
        if args.len() != 1 {
            return CalcResult::new_args_number_error(cell);
        }
        let z = match self.get_number_no_bools(&args[0], cell) {
            Ok(f) => f,
            Err(s) => return s,
        };
        let dist = match Normal::new(0.0, 1.0) {
            Ok(d) => d,
            Err(_) => {
                return CalcResult::Error {
                    error: Error::ERROR,
                    origin: cell,
                    message: "Failed to construct standard normal distribution".to_string(),
                }
            }
        };

        let result = dist.cdf(z) - 0.5;

        if !result.is_finite() {
            return CalcResult::Error {
                error: Error::NUM,
                origin: cell,
                message: "Invalid result for GAUSS".to_string(),
            };
        }

        CalcResult::Number(result)
    }
}