Added MathMedian

Added MathMedian

Fix tests

crates/nu-command/src/default_context.rs

@@ -65,12 +65,13 @@ pub fn create_default_context() -> EngineState {
             MathCeil,
             MathFloor,
             MathMax,
+            MathMedian,
             MathMin,
+            MathMode,
             MathProduct,
             MathRound,
             MathSqrt,
             MathSum,
-            MathMode,
             Mkdir,
             Module,
             Mv,

crates/nu-command/src/math/median.rs

@@ -0,0 +1,121 @@
+use crate::math::avg::average;
+use crate::math::utils::run_with_function;
+use nu_protocol::ast::Call;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, Value};
+
+#[derive(Clone)]
+pub struct SubCommand;
+
+impl Command for SubCommand {
+    fn name(&self) -> &str {
+        "math median"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("math median")
+    }
+
+    fn usage(&self) -> &str {
+        "Gets the median of a list of numbers"
+    }
+
+    fn run(
+        &self,
+        _engine_state: &EngineState,
+        _stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
+        run_with_function(call, input, median)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Get the median of a list of numbers",
+            example: "[3 8 9 12 12 15] | math median",
+            result: Some(Value::Float {
+                val: 10.5,
+                span: Span::unknown(),
+            }),
+        }]
+    }
+}
+
+enum Pick {
+    MedianAverage,
+    Median,
+}
+
+pub fn median(values: &[Value], head: &Span) -> Result<Value, ShellError> {
+    let take = if values.len() % 2 == 0 {
+        Pick::MedianAverage
+    } else {
+        Pick::Median
+    };
+
+    let mut sorted = vec![];
+
+    for item in values {
+        sorted.push(item.clone());
+    }
+
+    if let Some(Err(values)) = values
+        .windows(2)
+        .map(|elem| {
+            if elem[0].partial_cmp(&elem[1]).is_none() {
+                return Err(ShellError::OperatorMismatch {
+                    op_span: *head,
+                    lhs_ty: elem[0].get_type(),
+                    lhs_span: elem[0].span()?,
+                    rhs_ty: elem[1].get_type(),
+                    rhs_span: elem[1].span()?,
+                });
+            }
+            Ok(elem[0].partial_cmp(&elem[1]).unwrap())
+        })
+        .find(|elem| elem.is_err())
+    {
+        return Err(values);
+    }
+
+    sorted.sort_by(|a, b| a.partial_cmp(b).unwrap());
+
+    match take {
+        Pick::Median => {
+            let idx = (values.len() as f64 / 2.0).floor() as usize;
+            let out = sorted
+                .get(idx)
+                .ok_or_else(|| ShellError::UnsupportedInput("Empty input".to_string(), *head))?;
+            Ok(out.clone())
+        }
+        Pick::MedianAverage => {
+            let idx_end = (values.len() / 2) as usize;
+            let idx_start = idx_end - 1;
+
+            let left = sorted
+                .get(idx_start)
+                .ok_or_else(|| ShellError::UnsupportedInput("Empty input".to_string(), *head))?
+                .clone();
+
+            let right = sorted
+                .get(idx_end)
+                .ok_or_else(|| ShellError::UnsupportedInput("Empty input".to_string(), *head))?
+                .clone();
+
+            average(&[left, right], head)
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(SubCommand {})
+    }
+}

crates/nu-command/src/math/mod.rs

@@ -4,6 +4,7 @@ mod ceil;
 pub mod command;
 mod floor;
 mod max;
+mod median;
 mod min;
 mod mode;
 mod product;
@@ -19,6 +20,7 @@ pub use ceil::SubCommand as MathCeil;
 pub use command::MathCommand as Math;
 pub use floor::SubCommand as MathFloor;
 pub use max::SubCommand as MathMax;
+pub use median::SubCommand as MathMedian;
 pub use min::SubCommand as MathMin;
 pub use mode::SubCommand as MathMode;
 pub use product::SubCommand as MathProduct;