Questions tagged [rust-polars]
271 questions
0
votes
1 answer
Rust Polars filter string input eagerly
I am trying to understand the 2 modes (lazy, eager) in Polars. I Found a way to do this lazily:
let out = df
.lazy()
.select([col("A"), col("B")
.filter(col("B").str().contains(input))])
.collect()
…
fvg
- 153
- 3
- 9
0
votes
1 answer
Polars with_context filter
I'm having a hard time understanding how to use the lazy with_context. The docs say
This allows expressions to also access columns from DataFrames that are not part of this one.
I want to filter a column based on a column from another frame, but I…
Cory Grinstead
- 511
- 3
- 16
0
votes
0 answers
Moved value of an expression in match statement
I'm generating and expression from a string.
Let us suppose to have a data frame with a close column ant I'm trying to compute all in parallel through expressions.
If the function receives a string "rolling_mean" I need to compute close -…
Sigi
- 53
- 8
0
votes
1 answer
How to convert a AnyValue::Datetime into a chrono Timestamp
I have use Polars in my Cargo.toml like this:
polars = { version = "0.24.3", features = ["lazy", "temporal", "ipc", "ipc_streaming", "dtype-datetime"] }
I have a Series extracted from a DataFrame that has datetime[ns] without a timezone. I now…
SirVer
- 1,397
- 1
- 16
- 15
0
votes
1 answer
Can I use indexing [start:end] in expressions instead of offset and length in polars
In Exp.slice, the only supported syntax is exp.slice(offset,length), but in some cases, something like exp[start:end] would be more convenient and consistent. So how to write exp[1:6] for exp.slice(1,5) just like it in pandas?
Facet
- 53
- 6
0
votes
1 answer
How to get an item in a polars dataframe column and put it back into the same column at a different location
Still new to polars and rust ... so here is a nooby question:
How do I access a value within a DataFrame at a specific location.
How do I overwrite a value within a DataFrame at a specific location.
Here is a NON-WORKING code:
use…
Robert
- 131
- 1
- 7
0
votes
1 answer
How to pass variable from one method to another in impl (in Rust)
Specific Question
I need to pass csv variable from load_csv function to operations function.
Code
use polars::{
prelude::{CsvReader, SerReader},
frame::DataFrame,
error::PolarsResult
};
struct Boilerplate {}
impl Boilerplate {
fn…
S3emingly
- 15
- 5
0
votes
0 answers
How to process a column of list_items
I have a DataFrame with a ListType column.
Now I am trying to find a way to process each list within that column.
If I could convert the list to a vector (ideally without unpacking the list and then re-packing it into a vector ... is there such a…
Robert
- 131
- 1
- 7
0
votes
0 answers
How to use a groupby_column_item in alias naming of a new column?
Trying to find out if there is a way to use a groupby column in naming an alias after an aggregate:
Could not find anything here on SO / Reddit etc.
Could I use an EXPR in the alias function?
Thanks for any help :)
use polars::prelude::*;
fn main()…
Robert
- 131
- 1
- 7
0
votes
2 answers
How to merge two DataFrames with different columns / sizes
Looking for a way to combine two DataFrames.
df1:
shape: (2, 2)
┌────────┬──────────────────────┐
│ Fruit ┆ Phosphorus (mg/100g) │
│ --- ┆ --- │
│ str ┆ i32 │
╞════════╪══════════════════════╡
│ Apple ┆ 11 …
Robert
- 131
- 1
- 7
0
votes
1 answer
How do I serialize Polars DataFrame Row/HashMap of `AnyValue` into JSON?
I have a row of a polars dataframe created using iterators reading a parquet file from this method: Iterate over rows polars rust
I have constructed a HashMap that represents an individual row and I would like to now convert that row into JSON.
This…
Al Johri
- 1,729
- 22
- 23
0
votes
0 answers
How to implement frame_equal_missing with tolerance (like pandas)?
assert!(expected.frame_equal_missing(&res1)); is failing when using pct_change.
because of float rounding differences (a-b)/b can be different from a/b - 1
How can I frame_equal_missing with a tolerance like pandas?
let df = df! [
"A" …
MBr
- 3
- 4
0
votes
4 answers
Combine different values of multiple columns into one column
Need help to "translate" a python example to rust. The python example was given here
Here is the code snippet I try to make work:
use polars::prelude::*;
fn main() {
let s1 = Series::new("Fruit", &["Apple", "Apple", "Pear"]);
let s2 =…
Robert
- 131
- 1
- 7
0
votes
1 answer
How to create a polars-Series from a vector of options
I am a little confused. Creating a polars series with a vector of "simple" options
Vec>
works ... but a vector of options with complex values (e.g. vectors / arrays) does not?!
Vec>>
Why? ... and how to make it work?
use…
Robert
- 131
- 1
- 7
0
votes
1 answer
How to convert rows into columns given an arbitrary step size in polars (in a single step)?
I've managed to solve this problem in two steps.
import polars as pl
text = "a brown fox jumps over a lazy dog's head"
step = 3
df = pl.DataFrame({"a":text.split(" ")})
first = df.filter(pl.arange(0, pl.count())%step==0)
second =…
pedrosaurio
- 4,708
- 11
- 39
- 53