Support average for tables.

crates/nu-cli/src/cli.rs

@@ -344,6 +344,7 @@ pub fn create_default_context(
             whole_stream_command(Headers),
             // Data processing
             whole_stream_command(Histogram),
+            whole_stream_command(Average),
             whole_stream_command(Sum),
             // File format output
             whole_stream_command(To),

crates/nu-cli/src/commands.rs

@@ -8,6 +8,7 @@ pub(crate) mod alias;
 pub(crate) mod append;
 pub(crate) mod args;
 pub(crate) mod autoview;
+pub(crate) mod average;
 pub(crate) mod build_string;
 pub(crate) mod cal;
 pub(crate) mod calc;
@@ -133,6 +134,7 @@ pub(crate) use command::{
 
 pub(crate) use alias::Alias;
 pub(crate) use append::Append;
+pub(crate) use average::Average;
 pub(crate) use build_string::BuildString;
 pub(crate) use cal::Cal;
 pub(crate) use calc::Calc;

crates/nu-cli/src/commands/average.rs

@@ -0,0 +1,172 @@
+use crate::commands::WholeStreamCommand;
+use crate::prelude::*;
+use crate::utils::data_processing::{reducer_for, Reduce};
+use bigdecimal::FromPrimitive;
+use nu_errors::ShellError;
+use nu_protocol::hir::{convert_number_to_u64, Number, Operator};
+use nu_protocol::{
+    Dictionary, Primitive, ReturnSuccess, ReturnValue, Signature, UntaggedValue, Value,
+};
+use num_traits::identities::Zero;
+
+use indexmap::map::IndexMap;
+
+pub struct Average;
+
+#[async_trait]
+impl WholeStreamCommand for Average {
+    fn name(&self) -> &str {
+        "average"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("average")
+    }
+
+    fn usage(&self) -> &str {
+        "Average the values."
+    }
+
+    async fn run(
+        &self,
+        args: CommandArgs,
+        registry: &CommandRegistry,
+    ) -> Result<OutputStream, ShellError> {
+        average(RunnableContext {
+            input: args.input,
+            registry: registry.clone(),
+            shell_manager: args.shell_manager,
+            host: args.host,
+            ctrl_c: args.ctrl_c,
+            name: args.call_info.name_tag,
+            raw_input: args.raw_input,
+        })
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Average a list of numbers",
+            example: "echo [100 0 100 0] | average",
+            result: Some(vec![UntaggedValue::decimal(50).into()]),
+        }]
+    }
+}
+
+fn average(
+    RunnableContext {
+        mut input, name, ..
+    }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let stream = async_stream! {
+        let mut values: Vec<Value> = input.drain_vec().await;
+        let action = reducer_for(Reduce::Sum);
+
+        if values.iter().all(|v| if let UntaggedValue::Primitive(_) = v.value {true} else {false}) {
+            match avg(&values, name) {
+                Ok(result) => yield ReturnSuccess::value(result),
+                Err(err) => yield Err(err),
+            }
+        } else {
+            let mut column_values = IndexMap::new();
+            for value in values {
+                match value.value {
+                    UntaggedValue::Row(row_dict) => {
+                        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()]);
+                        }
+                    },
+                    table => {},
+                };
+            }
+
+            let mut column_totals = IndexMap::new();
+            for (col_name, col_vals) in column_values {
+                match avg(&col_vals, &name) {
+                    Ok(result) => {
+                        column_totals.insert(col_name, result);
+                    }
+                    Err(err) => yield Err(err),
+                }
+            }
+            yield ReturnSuccess::value(
+                UntaggedValue::Row(Dictionary {entries: column_totals}).into_untagged_value())
+        }
+    };
+
+    let stream: BoxStream<'static, ReturnValue> = stream.boxed();
+
+    Ok(stream.to_output_stream())
+}
+
+fn avg(values: &[Value], name: impl Into<Tag>) -> Result<Value, ShellError> {
+    let name = name.into();
+
+    let sum = reducer_for(Reduce::Sum);
+
+    let number = BigDecimal::from_usize(values.len()).expect("expected a usize-sized bigdecimal");
+
+    let total_rows = UntaggedValue::decimal(number);
+    let total = sum(Value::zero(), values.to_vec())?;
+
+    match total {
+        Value {
+            value: UntaggedValue::Primitive(Primitive::Bytes(num)),
+            ..
+        } => {
+            let left = UntaggedValue::from(Primitive::Int(num.into()));
+            let result = crate::data::value::compute_values(Operator::Divide, &left, &total_rows);
+
+            match result {
+                Ok(UntaggedValue::Primitive(Primitive::Decimal(result))) => {
+                    let number = Number::Decimal(result);
+                    let number = convert_number_to_u64(&number);
+                    Ok(UntaggedValue::bytes(number).into_value(name))
+                }
+                Ok(_) => Err(ShellError::labeled_error(
+                    "could not calculate average of non-integer or unrelated types",
+                    "source",
+                    name,
+                )),
+                Err((left_type, right_type)) => Err(ShellError::coerce_error(
+                    left_type.spanned(name.span),
+                    right_type.spanned(name.span),
+                )),
+            }
+        }
+        Value {
+            value: UntaggedValue::Primitive(other),
+            ..
+        } => {
+            let left = UntaggedValue::from(other);
+            let result = crate::data::value::compute_values(Operator::Divide, &left, &total_rows);
+
+            match result {
+                Ok(value) => Ok(value.into_value(name)),
+                Err((left_type, right_type)) => Err(ShellError::coerce_error(
+                    left_type.spanned(name.span),
+                    right_type.spanned(name.span),
+                )),
+            }
+        }
+        _ => Err(ShellError::labeled_error(
+            "could not calculate average of non-integer or unrelated types",
+            "source",
+            name,
+        )),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Average;
+
+    #[test]
+    fn examples_work_as_expected() {
+        use crate::examples::test as test_examples;
+
+        test_examples(Average {})
+    }
+}

crates/nu-cli/tests/commands/average.rs

@@ -0,0 +1,26 @@
+use nu_test_support::{nu, pipeline};
+
+#[test]
+fn can_average_numbers() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats", pipeline(
+        r#"
+             open sgml_description.json
+             | get glossary.GlossDiv.GlossList.GlossEntry.Sections
+             | average
+             | echo $it
+         "#
+    ));
+
+    assert_eq!(actual.out, "101.5")
+}
+
+#[test]
+fn can_average_bytes() {
+    let actual = nu!(
+        cwd: "tests/fixtures/formats",
+        "ls | sort-by name | skip 1 | first 2 | get size | average | format \"{$it}\" | echo $it"
+    );
+
+    assert_eq!(actual.out, "1.6 KB");
+}

crates/nu-cli/tests/commands/mod.rs

@@ -1,5 +1,6 @@
 mod alias;
 mod append;
+mod average;
 mod cal;
 mod calc;
 mod cd;