Initial data commit

Task/Statistics-Basic/Rust/statistics-basic.rust

@@ -0,0 +1,70 @@
+#![feature(iter_arith)]
+extern crate rand;
+
+use rand::distributions::{IndependentSample, Range};
+
+pub fn mean(data: &[f32]) -> Option<f32> {
+    if data.is_empty() {
+        None
+    } else {
+        let sum: f32 = data.iter().sum();
+        Some(sum / data.len() as f32)
+    }
+}
+
+pub fn variance(data: &[f32]) -> Option<f32> {
+    if data.is_empty() {
+        None
+    } else {
+        let mean = mean(data).unwrap();
+        let mut sum = 0f32;
+        for &x in data {
+            sum += (x - mean).powi(2);
+        }
+        Some(sum / data.len() as f32)
+    }
+}
+
+pub fn standard_deviation(data: &[f32]) -> Option<f32> {
+    if data.is_empty() {
+        None
+    } else {
+        let variance = variance(data).unwrap();
+        Some(variance.sqrt())
+    }
+}
+
+fn print_histogram(width: u32, data: &[f32]) {
+    let mut histogram = [0; 10];
+    let len = histogram.len() as f32;
+    for &x in data {
+        histogram[(x * len) as usize] += 1;
+    }
+    let max_frequency = *histogram.iter().max().unwrap() as f32;
+    for (i, &frequency) in histogram.iter().enumerate() {
+        let bar_width = frequency as f32 * width as f32 / max_frequency;
+        print!("{:3.1}: ", i as f32 / len);
+        for _ in 0..bar_width as usize {
+            print!("*");
+        }
+        println!("");
+    }
+}
+
+fn main() {
+    let range = Range::new(0f32, 1f32);
+    let mut rng = rand::thread_rng();
+
+    for &number_of_samples in [1000, 10_000, 1_000_000].iter() {
+        let mut data = vec![];
+        for _ in 0..number_of_samples {
+            let x = range.ind_sample(&mut rng);
+            data.push(x);
+        }
+        println!("  Statistics for sample size {}", number_of_samples);
+        println!("Mean:               {:?}", mean(&data));
+        println!("Variance:           {:?}", variance(&data));
+        println!("Standard deviation: {:?}", standard_deviation(&data));
+        print_histogram(40, &data);
+    }
+}