Update the documentation of Row condition by Allex-Nik · Pull Request #1889 · Kotlin/dataframe

Allex-Nik · 2026-06-05T15:51:35Z

Add RowFilter and RowValueFilter as kinds of row conditions
Move DataRow samples from core to samples
Minor fixes

…Filter`, move samples from `core` to `samples`

Allex-Nik · 2026-06-05T16:15:11Z

+
+```kotlin
 // Row expression computes updated values
 df.update { weight }.at(1, 3, 4).with { prev()?.weight }


This is the original example. Do you think we should replace it with something more plausible?

Something like df.update { age }.at(1).with { it + 1 }?

I'd expand the original one - use both prev() and it and write about it in the comment

Allex-Nik · 2026-06-05T16:18:36Z

 ```kotlin
-// Row condition is used to filter rows by index
+// Row filter is used to filter rows by index
 df.filter { index() % 5 == 0 }


Also an original example. Do you think it's fine?

I'd replace with something more meaningful — name == && age > ...

And also, just here, I'd show the original df first with highlighted rows meeting the predicate.

Allex-Nik · 2026-06-05T16:22:00Z

+`RowValueFilter` is used via the `where` clause after selecting columns in functions
+such as [`update`](update.md), [`gather`](gather.md), and [`format`](format.md).
+Like `RowFilter`, it returns a `Boolean` indicating whether the row should be included in the result.
+However, unlike `RowFilter`, where both `this` and `it` refer to the current [`DataRow`](DataRow.md), 


Is it correct? As far as I understood, it's not that RowFilter works with entire rows and RowValueFilter works only with parts of rows. RowValueFilter can also access the whole row, it just additionally accesses the selected part of the row as it, right?

RowValueFilter works only with parts of rows

Why?

I do not think that RowValueFilter works only with parts of rows. In the second sentence I mean that as far as I understood, the distinction between RowFilter and RowValueFilter is not "one works only with entire rows and another works only with parts of rows" :)

Sorry, missread.
So, yes, totally correct! But not sure if RowValueFilter is used only via the where.

AndreiKingsley · 2026-06-15T09:28:40Z

+```
+
+<!---END-->
+<inline-frame src="resources/filter.html" width="100%"/>


AndreiKingsley · 2026-06-15T09:40:14Z

+and are used in [add](add.md), [filter](filter.md), [forEach](iterate.md), [update](update.md), and other operations.

-<!---FUN expressions-->
+Row expression signature: ```DataRow.(DataRow) -> T```. Row values can be accessed with or without ```it``` keyword. 


But below you show and example of update.with which has a different signature (it has a s type of selected column values)!
I believe we miss here Row-Value Expression definition

dataframe/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/documentation/ExpressionsGivenRow.kt

Line 83 in 5d17a73

interface RowValueExpression {

Could you please review it and rewrite it the same way as Row-Value Condition.

AndreiKingsley · 2026-06-15T10:18:06Z

+
+```kotlin
 // Row expression computes updated values
 df.update { weight }.at(1, 3, 4).with { prev()?.weight }


I'd expand the original one - use both prev() and it and write about it in the comment

AndreiKingsley · 2026-06-15T10:18:40Z

 ```kotlin
-// Row condition is used to filter rows by index
+// Row filter is used to filter rows by index
 df.filter { index() % 5 == 0 }


I'd replace with something more meaningful — name == && age > ...

AndreiKingsley · 2026-06-15T11:32:54Z

+`RowValueFilter` is used via the `where` clause after selecting columns in functions
+such as [`update`](update.md), [`gather`](gather.md), and [`format`](format.md).
+Like `RowFilter`, it returns a `Boolean` indicating whether the row should be included in the result.
+However, unlike `RowFilter`, where both `this` and `it` refer to the current [`DataRow`](DataRow.md), 


RowValueFilter works only with parts of rows

Why?

AndreiKingsley · 2026-06-15T11:39:06Z

@Allex-Nik let me fix #1888 so you can make examples prettier!

Allex-Nik added 2 commits June 5, 2026 17:41

Update documentation of Row conditions: add RowFilter and `RowValue…

5454a5a

…Filter`, move samples from `core` to `samples`

Minor fixes to the documentation of Row conditions

60e448a

Allex-Nik requested review from AndreiKingsley and zaleslaw June 5, 2026 15:51

Allex-Nik added the documentation Improvements or additions to documentation (not KDocs) label Jun 5, 2026

Allex-Nik commented Jun 5, 2026

View reviewed changes

Comment thread docs/StardustDocs/topics/concepts/DataRow.md

Allex-Nik commented Jun 5, 2026

View reviewed changes

Comment thread samples/src/test/kotlin/org/jetbrains/kotlinx/dataframe/samples/api/DataRowApiSamples.kt

AndreiKingsley requested changes Jun 15, 2026

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Allex-Nik commented Jun 5, 2026

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AndreiKingsley commented Jun 15, 2026

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