feat : implemented interquartile_range and also added respective test…

src/primary/interquartile_range.rs

@@ -0,0 +1,7 @@
+use crate::primary::quartiles;
+
+pub fn interquartile_range(values: &[f64]) -> Option<f64> {
+    let quartiles = quartiles(values)?;
+
+    Some(quartiles.q3 - quartiles.q1)
+}

src/primary/mod.rs

@@ -4,6 +4,7 @@ pub mod mode;
 pub mod quartiles;
 pub mod variance;
 pub mod std_deviation;
+pub mod interquartile_range;
 pub mod range;
 
 
@@ -13,5 +14,5 @@ pub use mode::mode;
 pub use quartiles::{Quartiles, quartiles};
 pub use variance::variance;
 pub use std_deviation::std_deviation;
-
-pub use range::range;
+pub use interquartile_range::interquartile_range;
+pub use range::range;

tests/interquartile_range.rs

@@ -0,0 +1,34 @@
+use rustats::primary::interquartile_range;
+
+#[test]
+fn empty_returns_none() {
+    assert_eq!(interquartile_range(&[]), None);
+}
+
+#[test]
+fn single_value_returns_zero() {
+    assert_eq!(
+        interquartile_range(&[10.0]),
+        Some(0.0)
+    );
+}
+
+#[test]
+fn odd_length_dataset() {
+    let values = [1.0, 2.0, 3.0, 4.0, 5.0];
+
+    assert_eq!(
+        interquartile_range(&values),
+        Some(3.0)
+    );
+}
+
+#[test]
+fn even_length_dataset() {
+    let values = [1.0, 2.0, 3.0, 4.0];
+
+    assert_eq!(
+        interquartile_range(&values),
+        Some(2.0)
+    );
+}