dark.vador's questions

尽管：

1. polar_lazy 0.44.2的阅读

2. 成功安装cargo add polars-lazy

以下代码会导致错误：

• 错误[E0433]：无法解析：legacy找不到arrow

• 错误[E0433]：无法解析：使用未声明的包或模块polars_core

• PolarsResult错误[E0412]：在此范围内找不到类型

• DataFrame错误[E0412]：在此范围内找不到类型

  use polars_core::prelude::*;
  use polars_core::df;
  use polars_lazy::prelude::*;
  use arrow::legacy::prelude::QuantileMethod;
  
  fn main() {
    let test = example()
    println!("show dataframe: {:?}", test);
  
  }
  
  fn example() -> PolarsResult<DataFrame> {
   let df = df!(
       "date" => ["2020-08-21", "2020-08-21", "2020-08-22", "2020-08-23", "2020-08-22"],
       "temp" => [20, 10, 7, 9, 1],
       "rain" => [0.2, 0.1, 0.3, 0.1, 0.01]
   )?;
  
   df.lazy()
   .group_by([col("date")])
   .agg([
       col("rain").min().alias("min_rain"),
       col("rain").sum().alias("sum_rain"),
       col("rain").quantile(lit(0.5), QuantileMethod::Nearest).alias("median_rain"),
   ])
   .sort(["date"], Default::default())
   .collect()
  }
  

注意：Cargo.toml

[dependencies]
arrow = "53.2.0"
polars-lazy = "0.44.2"