nushell/crates/nu-command/src/math/stddev.rs
JT 6cdfee3573
Move Value to helpers, separate span call (#10121)
# Description

As part of the refactor to split spans off of Value, this moves to using
helper functions to create values, and using `.span()` instead of
matching span out of Value directly.

Hoping to get a few more helping hands to finish this, as there are a
lot of commands to update :)

# User-Facing Changes
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---------

Co-authored-by: Darren Schroeder <343840+fdncred@users.noreply.github.com>
Co-authored-by: WindSoilder <windsoilder@outlook.com>
2023-09-03 07:27:29 -07:00

92 lines
2.7 KiB
Rust

use super::variance::compute_variance as variance;
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, Type, Value};
#[derive(Clone)]
pub struct SubCommand;
impl Command for SubCommand {
fn name(&self) -> &str {
"math stddev"
}
fn signature(&self) -> Signature {
Signature::build("math stddev")
.input_output_types(vec![(Type::List(Box::new(Type::Number)), Type::Number)])
.switch(
"sample",
"calculate sample standard deviation (i.e. using N-1 as the denominator)",
Some('s'),
)
.category(Category::Math)
}
fn usage(&self) -> &str {
"Returns the standard deviation of a list of numbers, or of each column in a table."
}
fn search_terms(&self) -> Vec<&str> {
vec![
"SD",
"standard",
"deviation",
"dispersion",
"variation",
"statistics",
]
}
fn run(
&self,
_engine_state: &EngineState,
_stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let sample = call.has_flag("sample");
run_with_function(call, input, compute_stddev(sample))
}
fn examples(&self) -> Vec<Example> {
vec![
Example {
description: "Compute the standard deviation of a list of numbers",
example: "[1 2 3 4 5] | math stddev",
result: Some(Value::test_float(std::f64::consts::SQRT_2)),
},
Example {
description: "Compute the sample standard deviation of a list of numbers",
example: "[1 2 3 4 5] | math stddev -s",
result: Some(Value::test_float(1.5811388300841898)),
},
]
}
}
pub fn compute_stddev(sample: bool) -> impl Fn(&[Value], Span, Span) -> Result<Value, ShellError> {
move |values: &[Value], span: Span, head: Span| {
// variance() produces its own usable error, so we can use `?` to propagated the error.
let variance = variance(sample)(values, span, head)?;
let val_span = variance.span();
match variance {
Value::Float { val, .. } => Ok(Value::float(val.sqrt(), val_span)),
Value::Int { val, .. } => Ok(Value::float((val as f64).sqrt(), val_span)),
other => Ok(other),
}
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn test_examples() {
use crate::test_examples;
test_examples(SubCommand {})
}
}