Add statistics on DataFrame support

[zaleslaw]

• std
• median
• percentile
• min
• max
• mean

[Copilot]

Pull Request Overview

This PR adds comprehensive support for statistical operations on DataFrames by introducing new functions and tests for mean, std, median, min, max, and percentile. Key changes include:

• New test cases in Kotlin for each statistical function.
• Updates to API methods and aggregator implementations with new interpretable annotations.
• Adjustments in loadInterpreter, Aggregators, and GroupBy modules to integrate the statistics operations.

Reviewed Changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
plugins/kotlin-dataframe/tests-gen/org/jetbrains/kotlin/fir/dataframe/DataFrameBlackBoxCodegenTestGenerated.java	Added new test methods for statistical operations.
plugins/kotlin-dataframe/testData/box/*.kt	New test files for std, percentile, min, median, mean, and max operations.
plugins/kotlin-dataframe/src/org/jetbrains/kotlinx/dataframe/plugin/loadInterpreter.kt	Imported and registered new aggregator implementations.
plugins/kotlin-dataframe/src/org/jetbrains/kotlinx/dataframe/plugin/impl/api/statistics.kt	Updated aggregator implementations to handle new statistics functions.
core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/statistics.kt	Added and updated tests for DataFrame statistics methods.
core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/impl/aggregation/aggregators/Aggregators.kt	Modified aggregator definitions for min, max, median, and percentile.
core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/*.kt	Added annotations and refinements for new API methods (std, percentile, min, median, mean, max).

[zaleslaw]

@koperagen I got this
`While analysing /percentile.kt:32:16: org.jetbrains.kotlinx.dataframe.plugin.InterpretationFrameworkError: ERROR: Different set of arguments
Implementation class: org.jetbrains.kotlinx.dataframe.plugin.impl.api.Percentile0@1f93c6b8
Not found in actual: []
Passed, but not expected: [percentile]
add arguments to an interpeter:
[RefinedArgument(name=percentile, expression=org.jetbrains.kotlin.fir.expressions.impl.FirLiteralExpressionImpl@6ecaf7ce)]

org.jetbrains.kotlin.util.FileAnalysisException: While analysing /percentile.kt:32:16: org.jetbrains.kotlinx.dataframe.plugin.InterpretationFrameworkError: ERROR: Different set of arguments
Implementation class: org.jetbrains.kotlinx.dataframe.plugin.impl.api.Percentile0@1f93c6b8
Not found in actual: []
Passed, but not expected: [percentile]
add arguments to an interpeter:
[RefinedArgument(name=percentile, expression=org.jetbrains.kotlin.fir.expressions.impl.FirLiteralExpressionImpl@6ecaf7ce)]`

but for running this code val res0 = personsDf.percentile(percentile = 30.0) what I'm doing wrong?

[koperagen]

Very cool! Please check my comment, and let's wait for the build to finish. Otherwise looks good

[koperagen]

val df = dataFrameOf("a")(1, 2, 3)
df.groupBy { a named "b" }.sum { a }

Do you have a test for this?
it'll be columns b and a - surprisingly when only one column is selected in sum(ColumnsSelector), aggregated column will have its name