Questions tagged [rust-polars]
271 questions
2
votes
0 answers
Is there a way to use a specific global string cache after running reset_string_cache() in rust polars
Running below code we get two global string cache as I have used reset_string_cache() before creating out2.
Is it possible to create another categorical variable with same global string cache as used in out1 after using reset_string_cache()?
use…
Kushdesh
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2
votes
1 answer
LazyFrame: How to do string manipulation on values in a single column
I want to change all string values in a LazyFrame-Column.
e.g. from "alles ok" ==> to "ALLES OK"
I see that a series has a function to do it:
polars.internals.series.StringNameSpace.to_uppercase
Q: What is the proper way to apply a string (or Date)…
Robert
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2
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1 answer
POLARS Dataframe innerJOIN in RUST
RUST / POLARS nooby question :)
I can not get the "inner_join" to work:
use polars::prelude::*;
use std::fs::File;
use std::path::PathBuf;
use std::env;
fn main() -> std::io::Result<()> {
let mut root = env::current_dir().unwrap();
let…
Robert
- 131
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- 7
2
votes
1 answer
How to create a column with the lengths of strings from a different column in Polars Rust?
I'm trying to replicate one of the Polars Python examples in Rust but seem to have hit a wall. In the Python docs there is an example which creates a new column with the lengths of the strings from another column. So for example, column B will…
Stefan
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2
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0 answers
What is an efficient way of loop through rows of a polars LazyFrame?
I have a large Parquet file with just a few columns, and I'd like apply a function to each row of the Paruqet file. What is an efficient way of doing that? By efficient, I mean 2 things.
The code runs fast.
The code doesn't load the while file into…
Benjamin Du
- 1,391
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2
votes
3 answers
How to apply a function to multiple columns of a polars DataFrame in Rust
I'd like to apply a user-define function which takes a few inputs (corresponding some columns in a polars DataFrame) to some columns of a polars DataFrame in Rust. The pattern that I'm using is as below. I wonder is this the best practice?
fn…
Benjamin Du
- 1,391
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- 17
- 25
2
votes
2 answers
window agg over one value, but return another via Polars
I am trying to use polars to do a window aggregate over one value, but map it back to another.
For example, if i wanted to get the name of the max value in a group, instead of (or in combination to) just the max value.
assuming an input of something…
Cory Grinstead
- 511
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2
votes
1 answer
How to loc value in Rust Polars?
In Pandas or Polars-Python, we can loc a value by using iloc loc or [1,2]. How could we do the same thing in Polars with Rust?
Hakase
- 211
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2
votes
1 answer
How to get a Vec from polars Series or ChunkedArray?
In Rust Polars, how to cast a Series or ChunkedArray to a Vec?
Hakase
- 211
- 1
- 12
2
votes
1 answer
How to the get the first n% of a group in polars?
Q1: In polars-rust, when you do .groupby().agg() , we can use .head(10) to get the first 10 elements in a column. But if the groups have different lengths and I need to get first 20% elements in each group (like 0-24 elements in a 120 elements…
Hakase
- 211
- 1
- 12
2
votes
2 answers
Is there a way to apply a UDF function returning multiple values in Rust polars?
I'm trying to use polars to apply a function from another library across each row of an input. I can't find any examples or tests of using an Expr to apply a function, even when it has one return value; so I'm lost.
It's taking an input dataframe…
Dominik Winecki
- 31
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2
votes
1 answer
In polars, can I create a categorical type with levels myself?
In Pandas, I can specify the levels of a Categorical type myself:
MyCat = pd.CategoricalDtype(categories=['A','B','C'], ordered=True)
my_data = pd.Series(['A','A','B'], dtype=MyCat)
This means that
I can make sure that different columns and sets…
Jarrad
- 927
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2
votes
2 answers
How to define types of columns while loading dataframe in polars?
I'm using polars and I would like to define the type of the columns while loading a dataframe. In pandas, I can use dtype:
df=pd.read_csv("iris.csv", dtype={'petal_length':str})
I'm trying to do the same thing in polars, but without success until…
Lucas
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1
vote
1 answer
Polars: Date formatting with 'custom' nanosecond precision
I am new to polars, and i was trying to convert a flat file datetime type column to a dataframe column with 1 nanosecond precision. For example:
1974-08-08 16:28:51 => 1974-08-08 16:28:51.0
1997-12-12 17:56:19 => 1997-12-12 17:56:19.0
Flat…
1
vote
0 answers
Polars - avoid repeatedly doing a groupby_dynamic for similar operations? How to rewrite the Exprs?
I have a large dataframe that I am doing a groupby_dynamic operation on, and then doing an aggregation that combined the columns in each group, down to a single boolean value.
Ultimately, I have to do this operation many times, as it is part of a…
Andrew P.
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