2020-07-14 21:15:02 +02:00
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use crate::commands::math::utils::run_with_function;
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use crate::commands::WholeStreamCommand;
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use crate::data::value::compute_values;
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use crate::prelude::*;
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2020-08-04 00:47:19 +02:00
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use bigdecimal::FromPrimitive;
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2020-07-14 21:15:02 +02:00
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use nu_errors::ShellError;
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use nu_protocol::{hir::Operator, Primitive, Signature, UntaggedValue, Value};
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pub struct SubCommand;
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#[async_trait]
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impl WholeStreamCommand for SubCommand {
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fn name(&self) -> &str {
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"math variance"
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}
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fn signature(&self) -> Signature {
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Signature::build("math variance")
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}
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fn usage(&self) -> &str {
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"Finds the variance of a list of numbers or tables"
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}
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async fn run(
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&self,
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args: CommandArgs,
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registry: &CommandRegistry,
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) -> Result<OutputStream, ShellError> {
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run_with_function(
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RunnableContext {
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input: args.input,
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registry: registry.clone(),
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shell_manager: args.shell_manager,
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host: args.host,
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ctrl_c: args.ctrl_c,
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current_errors: args.current_errors,
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name: args.call_info.name_tag,
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raw_input: args.raw_input,
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},
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variance,
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)
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.await
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}
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fn examples(&self) -> Vec<Example> {
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vec![Example {
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description: "Get the variance of a list of numbers",
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example: "echo [1 2 3 4 5] | math variance",
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result: Some(vec![UntaggedValue::decimal(2).into()]),
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}]
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}
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}
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fn sum_of_squares(values: &[Value], name: &Tag) -> Result<Value, ShellError> {
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let n = BigDecimal::from_usize(values.len()).ok_or_else(|| {
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ShellError::labeled_error(
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"could not convert to big decimal",
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"could not convert to big decimal",
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&name.span,
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)
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})?;
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2020-08-04 00:47:19 +02:00
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let mut sum_x = UntaggedValue::int(0).into_untagged_value();
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let mut sum_x2 = UntaggedValue::int(0).into_untagged_value();
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2020-07-14 21:15:02 +02:00
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for value in values {
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let v = match value {
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Value {
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value: UntaggedValue::Primitive(Primitive::Filesize(num)),
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..
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} => {
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UntaggedValue::from(Primitive::Int(num.clone().into()))
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},
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Value {
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value: UntaggedValue::Primitive(num),
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..
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} => {
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UntaggedValue::from(num.clone())
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},
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_ => {
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return Err(ShellError::labeled_error(
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"Attempted to compute the sum of squared values of a value that cannot be summed or squared.",
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"value appears here",
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value.tag.span,
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))
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}
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};
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let v_squared = compute_values(Operator::Multiply, &v, &v);
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match v_squared {
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// X^2
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2020-08-04 00:47:19 +02:00
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Ok(x2) => {
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sum_x2 = match compute_values(Operator::Plus, &sum_x2, &x2) {
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Ok(v) => v.into_untagged_value(),
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Err((left_type, right_type)) => {
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return Err(ShellError::coerce_error(
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left_type.spanned(name.span),
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right_type.spanned(name.span),
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))
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}
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};
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}
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2020-07-14 21:15:02 +02:00
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Err((left_type, right_type)) => {
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return Err(ShellError::coerce_error(
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left_type.spanned(value.tag.span),
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right_type.spanned(value.tag.span),
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))
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}
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};
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2020-08-04 00:47:19 +02:00
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sum_x = match compute_values(Operator::Plus, &sum_x, &v) {
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Ok(v) => v.into_untagged_value(),
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Err((left_type, right_type)) => {
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return Err(ShellError::coerce_error(
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left_type.spanned(name.span),
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right_type.spanned(name.span),
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))
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}
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};
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2020-07-14 21:15:02 +02:00
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}
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let sum_x_squared = match compute_values(Operator::Multiply, &sum_x, &sum_x) {
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Ok(v) => v.into_untagged_value(),
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Err((left_type, right_type)) => {
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return Err(ShellError::coerce_error(
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left_type.spanned(name.span),
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right_type.spanned(name.span),
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))
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}
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};
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let sum_x_squared_div_n = match compute_values(Operator::Divide, &sum_x_squared, &n.into()) {
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Ok(v) => v.into_untagged_value(),
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Err((left_type, right_type)) => {
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return Err(ShellError::coerce_error(
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left_type.spanned(name.span),
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right_type.spanned(name.span),
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))
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}
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};
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let ss = match compute_values(Operator::Minus, &sum_x2, &sum_x_squared_div_n) {
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Ok(v) => v.into_untagged_value(),
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Err((left_type, right_type)) => {
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return Err(ShellError::coerce_error(
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left_type.spanned(name.span),
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right_type.spanned(name.span),
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))
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}
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};
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Ok(ss)
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}
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pub fn variance(values: &[Value], name: &Tag) -> Result<Value, ShellError> {
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let ss = sum_of_squares(values, name)?;
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let n = BigDecimal::from_usize(values.len()).ok_or_else(|| {
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ShellError::labeled_error(
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"could not convert to big decimal",
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"could not convert to big decimal",
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&name.span,
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)
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})?;
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let variance = compute_values(Operator::Divide, &ss, &n.into());
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match variance {
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Ok(value) => Ok(value.into_value(name)),
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Err((_, _)) => Err(ShellError::labeled_error(
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"could not calculate variance of non-integer or unrelated types",
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"source",
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name,
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)),
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}
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}
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#[cfg(test)]
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mod tests {
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use super::SubCommand;
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#[test]
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fn examples_work_as_expected() {
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use crate::examples::test as test_examples;
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test_examples(SubCommand {})
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}
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}
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