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n_null.rs
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n_null.rs
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use super::super::values::{Column, NuDataFrame};
use nu_protocol::{
ast::Call,
engine::{Command, EngineState, Stack},
Category, Example, PipelineData, ShellError, Signature, Span, Type, Value,
};
#[derive(Clone)]
pub struct NNull;
impl Command for NNull {
fn name(&self) -> &str {
"count-null"
}
fn usage(&self) -> &str {
"Counts null values"
}
fn signature(&self) -> Signature {
Signature::build(self.name())
.input_type(Type::Custom("dataframe".into()))
.output_type(Type::Custom("dataframe".into()))
.category(Category::Custom("dataframe".into()))
}
fn examples(&self) -> Vec<Example> {
vec![Example {
description: "Counts null values",
example: r#"let s = ([1 1 0 0 3 3 4] | into df);
($s / $s) | count-null"#,
result: Some(
NuDataFrame::try_from_columns(vec![Column::new(
"count_null".to_string(),
vec![Value::test_int(2)],
)])
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
}]
}
fn run(
&self,
engine_state: &EngineState,
stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
command(engine_state, stack, call, input)
}
}
fn command(
_engine_state: &EngineState,
_stack: &mut Stack,
call: &Call,
input: PipelineData,
) -> Result<PipelineData, ShellError> {
let df = NuDataFrame::try_from_pipeline(input, call.head)?;
let res = df.as_series(call.head)?.null_count();
let value = Value::int(res as i64, call.head);
NuDataFrame::try_from_columns(vec![Column::new("count_null".to_string(), vec![value])])
.map(|df| PipelineData::Value(NuDataFrame::into_value(df, call.head), None))
}
#[cfg(test)]
mod test {
use super::super::super::test_dataframe::test_dataframe;
use super::*;
#[test]
fn test_examples() {
test_dataframe(vec![Box::new(NNull {})])
}
}