<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class ModelLinear extends CI_Model {

    public function get_cases_data() {
        // Data jumlah kasus stunting
        return [
            'years' => [2020, 2021, 2022, 2023, 2024],
            'cases' => [156, 86, 43, 66, 62]
        ];
    }

    public function calculate_regression($years, $cases) {
        $n = count($years);
        $sum_x = array_sum($years);
        $sum_y = array_sum($cases);
        $sum_x_squared = array_sum(array_map(function($x) { return $x * $x; }, $years));
        $sum_xy = array_sum(array_map(function($x, $y) { return $x * $y; }, $years, $cases));

        $slope = ($n * $sum_xy - $sum_x * $sum_y) / ($n * $sum_x_squared - $sum_x * $sum_x);
        $intercept = ($sum_y - $slope * $sum_x) / $n;

        return [
            'slope' => $slope,
            'intercept' => $intercept
        ];
    }

    public function forecast($slope, $intercept, $next_year) {
        return $slope * $next_year + $intercept;
    }
}