Add Interquartile Range (#633)

Author: cyrixninja

DIRECTORY.md

@@ -183,6 +183,7 @@
     * [Huber Loss](https://github.com/TheAlgorithms/Rust/blob/master/src/math/huber_loss.rs)
     * [Interest](https://github.com/TheAlgorithms/Rust/blob/master/src/math/interest.rs)
     * [Interpolation](https://github.com/TheAlgorithms/Rust/blob/master/src/math/interpolation.rs)
+    * [Interquartile Range](https://github.com/TheAlgorithms/Rust/blob/master/src/math/interquartile_range.rs)
     * [Karatsuba Multiplication](https://github.com/TheAlgorithms/Rust/blob/master/src/math/karatsuba_multiplication.rs)
     * [Lcm Of N Numbers](https://github.com/TheAlgorithms/Rust/blob/master/src/math/lcm_of_n_numbers.rs)
     * [Leaky Relu](https://github.com/TheAlgorithms/Rust/blob/master/src/math/leaky_relu.rs)

src/math/interquartile_range.rs

@@ -0,0 +1,85 @@
+// Author : cyrixninja
+// Interquartile Range  : An implementation of interquartile range (IQR) which is a measure of statistical
+//                        dispersion, which is the spread of the data.
+// Wikipedia Reference  : https://en.wikipedia.org/wiki/Interquartile_range
+
+use std::cmp::Ordering;
+
+pub fn find_median(numbers: &[f64]) -> f64 {
+    let mut numbers = numbers.to_vec();
+    numbers.sort_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal));
+
+    let length = numbers.len();
+    let mid = length / 2;
+
+    if length % 2 == 0 {
+        (numbers[mid - 1] + numbers[mid]) / 2.0
+    } else {
+        numbers[mid]
+    }
+}
+
+pub fn interquartile_range(numbers: &[f64]) -> f64 {
+    if numbers.is_empty() {
+        panic!("Error: The list is empty. Please provide a non-empty list.");
+    }
+
+    let mut numbers = numbers.to_vec();
+    numbers.sort_by(|a, b| a.partial_cmp(b).unwrap_or(Ordering::Equal));
+
+    let length = numbers.len();
+    let mid = length / 2;
+    let (q1, q3) = if length % 2 == 0 {
+        let first_half = &numbers[0..mid];
+        let second_half = &numbers[mid..length];
+        (find_median(first_half), find_median(second_half))
+    } else {
+        let first_half = &numbers[0..mid];
+        let second_half = &numbers[mid + 1..length];
+        (find_median(first_half), find_median(second_half))
+    };
+
+    q3 - q1
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_find_median() {
+        let numbers1 = vec![1.0, 2.0, 2.0, 3.0, 4.0];
+        assert_eq!(find_median(&numbers1), 2.0);
+
+        let numbers2 = vec![1.0, 2.0, 2.0, 3.0, 4.0, 4.0];
+        assert_eq!(find_median(&numbers2), 2.5);
+
+        let numbers3 = vec![-1.0, 2.0, 0.0, 3.0, 4.0, -4.0];
+        assert_eq!(find_median(&numbers3), 1.0);
+
+        let numbers4 = vec![1.1, 2.2, 2.0, 3.3, 4.4, 4.0];
+        assert_eq!(find_median(&numbers4), 2.75);
+    }
+
+    #[test]
+    fn test_interquartile_range() {
+        let numbers1 = vec![4.0, 1.0, 2.0, 3.0, 2.0];
+        assert_eq!(interquartile_range(&numbers1), 2.0);
+
+        let numbers2 = vec![-2.0, -7.0, -10.0, 9.0, 8.0, 4.0, -67.0, 45.0];
+        assert_eq!(interquartile_range(&numbers2), 17.0);
+
+        let numbers3 = vec![-2.1, -7.1, -10.1, 9.1, 8.1, 4.1, -67.1, 45.1];
+        assert_eq!(interquartile_range(&numbers3), 17.2);
+
+        let numbers4 = vec![0.0, 0.0, 0.0, 0.0, 0.0];
+        assert_eq!(interquartile_range(&numbers4), 0.0);
+    }
+
+    #[test]
+    #[should_panic(expected = "Error: The list is empty. Please provide a non-empty list.")]
+    fn test_interquartile_range_empty_list() {
+        let numbers: Vec<f64> = vec![];
+        interquartile_range(&numbers);
+    }
+}

src/math/mod.rs

@@ -33,6 +33,7 @@ mod greatest_common_divisor;
 mod huber_loss;
 mod interest;
 mod interpolation;
+mod interquartile_range;
 mod karatsuba_multiplication;
 mod lcm_of_n_numbers;
 mod leaky_relu;
@@ -112,6 +113,7 @@ pub use self::greatest_common_divisor::{
 pub use self::huber_loss::huber_loss;
 pub use self::interest::{compound_interest, simple_interest};
 pub use self::interpolation::{lagrange_polynomial_interpolation, linear_interpolation};
+pub use self::interquartile_range::interquartile_range;
 pub use self::karatsuba_multiplication::multiply;
 pub use self::lcm_of_n_numbers::lcm;
 pub use self::leaky_relu::leaky_relu;