use crate::prelude::*;
use bigdecimal::FromPrimitive;
use nu_data::value::compute_values;
use nu_engine::WholeStreamCommand;
use nu_errors::ShellError;
use nu_protocol::{
hir::Operator, Dictionary, Primitive, ReturnSuccess, Signature, UntaggedValue, Value,
};
use nu_source::Tagged;
pub struct SubCommand;
#[derive(Deserialize)]
struct Arguments {
sample: Tagged<bool>,
}
#[async_trait]
impl WholeStreamCommand for SubCommand {
fn name(&self) -> &str {
"math variance"
}
fn signature(&self) -> Signature {
Signature::build("math variance").switch("sample", "calculate sample variance", Some('s'))
}
fn usage(&self) -> &str {
"Finds the variance of a list of numbers or tables"
}
async fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
let name = args.call_info.name_tag.clone();
let (Arguments { sample }, mut input) = args.process().await?;
let values: Vec<Value> = input.drain_vec().await;
let n = if let Tagged { item: true, .. } = sample {
values.len() - 1
} else {
values.len()
};
let res = if values.iter().all(|v| v.is_primitive()) {
compute_variance(&values, n, &name)
} else {
let mut column_values = IndexMap::new();
for value in values {
if let UntaggedValue::Row(row_dict) = &value.value {
for (key, value) in row_dict.entries.iter() {
column_values
.entry(key.clone())
.and_modify(|v: &mut Vec<Value>| v.push(value.clone()))
.or_insert(vec![value.clone()]);
}
}
}
let mut column_totals = IndexMap::new();
for (col_name, col_vals) in column_values {
if let Ok(out) = compute_variance(&col_vals, n, &name) {
column_totals.insert(col_name, out);
}
}
if column_totals.keys().len() == 0 {
return Err(ShellError::labeled_error(
"Attempted to compute values that can't be operated on",
"value appears here",
name.span,
));
}
Ok(UntaggedValue::Row(Dictionary {
entries: column_totals,
})
.into_untagged_value())
}?;
if res.value.is_table() {
Ok(OutputStream::from(
res.table_entries()
.map(|v| ReturnSuccess::value(v.clone()))
.collect::<Vec<_>>(),
))
} else {
Ok(OutputStream::one(ReturnSuccess::value(res)))
}
}
fn examples(&self) -> Vec<Example> {
vec![
Example {
description: "Get the variance of a list of numbers",
example: "echo [1 2 3 4 5] | math variance",
result: Some(vec![UntaggedValue::decimal_from_float(
2.0,
Span::unknown(),
)
.into()]),
},
Example {
description: "Get the sample variance of a list of numbers",
example: "echo [1 2 3 4 5] | math variance -s",
result: Some(vec![UntaggedValue::decimal_from_float(
2.5,
Span::unknown(),
)
.into()]),
},
]
}
}
fn sum_of_squares(values: &[Value], name: &Tag) -> Result<Value, ShellError> {
let n = BigDecimal::from_usize(values.len()).ok_or_else(|| {
ShellError::labeled_error(
"could not convert to big decimal",
"could not convert to big decimal",
&name.span,
)
})?;
let mut sum_x = UntaggedValue::int(0).into_untagged_value();
let mut sum_x2 = UntaggedValue::int(0).into_untagged_value();
for value in values {
let v = match value {
Value {
value: UntaggedValue::Primitive(Primitive::Filesize(num)),
..
} => {
UntaggedValue::from(Primitive::Int(num.clone()))
},
Value {
value: UntaggedValue::Primitive(num),
..
} => {
UntaggedValue::from(num.clone())
},
_ => {
return Err(ShellError::labeled_error(
"Attempted to compute the sum of squared values of a value that cannot be summed or squared.",
"value appears here",
value.tag.span,
))
}
};
let v_squared = compute_values(Operator::Multiply, &v, &v);
match v_squared {
Ok(x2) => {
sum_x2 = match compute_values(Operator::Plus, &sum_x2, &x2) {
Ok(v) => v.into_untagged_value(),
Err((left_type, right_type)) => {
return Err(ShellError::coerce_error(
left_type.spanned(name.span),
right_type.spanned(name.span),
))
}
};
}
Err((left_type, right_type)) => {
return Err(ShellError::coerce_error(
left_type.spanned(value.tag.span),
right_type.spanned(value.tag.span),
))
}
};
sum_x = match compute_values(Operator::Plus, &sum_x, &v) {
Ok(v) => v.into_untagged_value(),
Err((left_type, right_type)) => {
return Err(ShellError::coerce_error(
left_type.spanned(name.span),
right_type.spanned(name.span),
))
}
};
}
let sum_x_squared = match compute_values(Operator::Multiply, &sum_x, &sum_x) {
Ok(v) => v.into_untagged_value(),
Err((left_type, right_type)) => {
return Err(ShellError::coerce_error(
left_type.spanned(name.span),
right_type.spanned(name.span),
))
}
};
let sum_x_squared_div_n = match compute_values(Operator::Divide, &sum_x_squared, &n.into()) {
Ok(v) => v.into_untagged_value(),
Err((left_type, right_type)) => {
return Err(ShellError::coerce_error(
left_type.spanned(name.span),
right_type.spanned(name.span),
))
}
};
let ss = match compute_values(Operator::Minus, &sum_x2, &sum_x_squared_div_n) {
Ok(v) => v.into_untagged_value(),
Err((left_type, right_type)) => {
return Err(ShellError::coerce_error(
left_type.spanned(name.span),
right_type.spanned(name.span),
))
}
};
Ok(ss)
}
#[cfg(test)]
pub fn variance(values: &[Value], name: &Tag) -> Result<Value, ShellError> {
compute_variance(values, values.len(), name)
}
pub fn compute_variance(values: &[Value], n: usize, name: &Tag) -> Result<Value, ShellError> {
let ss = sum_of_squares(values, name)?;
let n = BigDecimal::from_usize(n).ok_or_else(|| {
ShellError::labeled_error(
"could not convert to big decimal",
"could not convert to big decimal",
&name.span,
)
})?;
let variance = compute_values(Operator::Divide, &ss, &n.into());
match variance {
Ok(value) => Ok(value.into_value(name)),
Err((_, _)) => Err(ShellError::labeled_error(
"could not calculate variance of non-integer or unrelated types",
"source",
name,
)),
}
}
#[cfg(test)]
mod tests {
use super::ShellError;
use super::SubCommand;
#[test]
fn examples_work_as_expected() -> Result<(), ShellError> {
use crate::examples::test as test_examples;
test_examples(SubCommand {})
}
}