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cmd(df/first): returns the first row by default. #6312

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merged 1 commit into from Aug 13, 2022
Merged

cmd(df/first): returns the first row by default. #6312

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56 changes: 40 additions & 16 deletions crates/nu-command/src/dataframe/eager/first.rs
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@@ -1,4 +1,4 @@
use super::super::values::{utils::DEFAULT_ROWS, Column, NuDataFrame};
use super::super::values::{Column, NuDataFrame};
use nu_engine::CallExt;
use nu_protocol::{
ast::Call,
Expand All @@ -15,30 +15,54 @@ impl Command for FirstDF {
}

fn usage(&self) -> &str {
"Creates new dataframe with first rows"
"Show only the first number of rows."
}

fn signature(&self) -> Signature {
Signature::build(self.name())
.optional("rows", SyntaxShape::Int, "Number of rows for head")
.optional(
"rows",
SyntaxShape::Int,
"starting from the front, the number of rows to return",
)
.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: "Create new dataframe with head rows",
example: "[[a b]; [1 2] [3 4]] | into df | first 1",
result: Some(
NuDataFrame::try_from_columns(vec![
Column::new("a".to_string(), vec![Value::test_int(1)]),
Column::new("b".to_string(), vec![Value::test_int(2)]),
])
.expect("simple df for test should not fail")
.into_value(Span::test_data()),
),
}]
vec![
Example {
description: "Return the first row of a dataframe",
example: "[[a b]; [1 2] [3 4]] | into df | first",
result: Some(
NuDataFrame::try_from_columns(vec![
Column::new("a".to_string(), vec![Value::test_int(1)]),
Column::new("b".to_string(), vec![Value::test_int(2)]),
])
.expect("should not fail")
.into_value(Span::test_data()),
),
},
Example {
description: "Return the first two rows of a dataframe",
example: "[[a b]; [1 2] [3 4]] | into df | first 2",
result: Some(
NuDataFrame::try_from_columns(vec![
Column::new(
"a".to_string(),
vec![Value::test_int(1), Value::test_int(3)],
),
Column::new(
"b".to_string(),
vec![Value::test_int(2), Value::test_int(4)],
),
])
.expect("should not fail")
.into_value(Span::test_data()),
),
},
]
}

fn run(
Expand All @@ -60,7 +84,7 @@ fn command(
df: NuDataFrame,
) -> Result<PipelineData, ShellError> {
let rows: Option<usize> = call.opt(engine_state, stack, 0)?;
let rows = rows.unwrap_or(DEFAULT_ROWS);
let rows = rows.unwrap_or(1);

let res = df.as_ref().head(Some(rows));
Ok(PipelineData::Value(
Expand Down