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

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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::{Category, 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").category(Category::Math)
}
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 {})
}
}