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#![feature(non_ascii_idents)] | |
fn main() { | |
std::env::args().nth(1) | |
.ok_or(format!("Usage: {} FILE", std::env::args().next().unwrap())) // File name | |
.and_then(|filename| { | |
std::fs::File::open(&filename) | |
.map_err(|e| (&e as &std::error::Error).description().to_string()) | |
}).map(|f| (f, String::new())) | |
.map(|(mut f, mut s)| ((&mut f as &mut std::io::Read).read_to_string(&mut s), s)) | |
.and_then(|(_, s)| s.lines().map(|line| { | |
line.parse::<u32>() | |
.map(|u| u as f32) | |
.map_err(|e| (&e as &std::error::Error).description().to_string()) | |
}).collect::<Result<Vec<f32>, String>>()) | |
.map(|vec| (vec.len() as f32, vec)) | |
.map(|(n, vec) : (f32, Vec<f32>)| { | |
(n, vec.into_iter().zip(1..).map(|(f, i)| (f32::ln(i as f32), f32::ln(f))) | |
.fold((0.0, 0.0, 0.0, 0.0, 0.0), | |
|(sum_x, sum_sqrx, sum_y, sum_sqry, sum_xy), (x, y)| { | |
(sum_x + x, sum_sqrx + x * x, sum_y + y, sum_sqry + y * y, sum_xy + x * y) | |
})) | |
}).map(|(n, (sum_x, sum_sqrx, sum_y, sum_sqry, sum_xy))| { | |
(sum_x / n, sum_sqrx / n, sum_y / n, sum_sqry / n, sum_xy / n) | |
}).map(|(x̅, s̅q̅r̅x̅, y̅, s̅q̅r̅y̅, x̅y̅)| { | |
((x̅y̅ - x̅ * y̅) / (s̅q̅r̅x̅ - x̅ * x̅), | |
(x̅y̅ - x̅ * y̅) * (x̅y̅ - x̅ * y̅) / ((s̅q̅r̅x̅ - x̅ * x̅) * (s̅q̅r̅y̅ - y̅ * y̅))) | |
}).map(|(m, sqrr)| println!("m: {}\nR²: {}", m, sqrr)) | |
.unwrap() | |
} |
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