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https://issues.apache.org/jira/browse/ARROW-6583?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wes McKinney updated ARROW-6583:
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Summary: [Rust] Question and Request for Examples of Array Operations
(was: Question and Request for Examples of Array Operations)
> [Rust] Question and Request for Examples of Array Operations
> ------------------------------------------------------------
>
> Key: ARROW-6583
> URL: https://issues.apache.org/jira/browse/ARROW-6583
> Project: Apache Arrow
> Issue Type: Improvement
> Components: Rust
> Reporter: Arthur Maciejewicz
> Priority: Minor
>
> Hi all, thank you for your excellent work on Arrow.
> As I was going through the example for the Rust Arrow implementation,
> specifically the read_csv example
> [https://github.com/apache/arrow/blob/master/rust/arrow/examples/read_csv.rs]
> , as well as the generated Rustdocs, and unit tests, it was not quite clear
> what the intended usage is for operations such as filtering and masking over
> Arrays.
> One particular use-case I'm interested in is finding all values in an Array
> such that x >= N for all x. I came across arrow::compute::array_ops::filter,
> which seems to be similar to what I want, although it's expecting a mask to
> already be constructed before performing the filter operation, and it was not
> obviously visible in the documentation, leading me to believe this might not
> be idiomatic usage.
> More generally, is the expectation for Arrays on the Rust side that they are
> just simple data abstractions, without exposing higher-order methods such as
> filtering/masking? Is the intent to leave that to users? If I missed some
> piece of documentation, please let me know. For my use-case I ended up trying
> something like:
> {code:java}
> let column = batch.column(0).as_any().downcast_ref::<Float64Array>().unwrap();
> let mut builder = BooleanBuilder::new(batch.num_rows());
> let N = 5.0;
> for i in 0..batch.num_rows() {
> if column.value(i).unwrap() > N {
> builder.append_value(true).unwrap();
> } else {
> builder.append_value(false).unwrap();
> }
> }
> let mask = builder.finish();
> let filtered_column = filter(column, mask);{code}
> If possible, could you provide examples of intended usage of Arrays? Thank
> you!
>
>
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