Finding a Row that Moved

2026-02-03 · Source: OR in an OB World · Field: Technology & Digital — Software Development & Engineering, Data Science & Analytics · Depth: Intermediate, short

Summary

This post addresses the challenge of programmatically scrolling a `DT` (DataTables) table in a Shiny application to a specific row after a user edit. The problem arises because user-initiated sorting and subsequent edits can cause a row's display position to change, potentially moving it out of view. The author distinguishes between "row index" (the unchanging underlying data row number) and "display index" (the row's current position in the sorted table). Initial attempts with AI coding assistants failed to fully resolve the issue. The solution involves a two-part approach: using a JavaScript snippet to handle the actual scrolling to a given display index, and an R-based method to determine the correct display index for an edited record, while also addressing a synchronization problem between `DT`'s table rendering and its `input$A_rows_all` vector update.

Key takeaway

For Shiny developers building interactive `DT` tables with external editing capabilities, you should anticipate and address row re-positioning after edits. Implement a combined R and JavaScript solution, ensuring that your scrolling logic waits for `DT`'s `input$TABLE_rows_all` vector to update. This prevents attempting to scroll to an incorrect or non-existent display index, improving user experience by keeping edited records in view.

Key insights

Scrolling to an edited row in a sorted Shiny `DT` table requires coordinating JavaScript and R with synchronization.

Principles

• Distinguish between data row index and display index.
• JavaScript handles client-side UI manipulation.
• Synchronization is critical for reactive Shiny components.

Method

Use JavaScript's `scrollIntoView` for scrolling, determine the display index via `input$TABLE_rows_all`, and wrap the scrolling logic in an `observeEvent(input$TABLE_rows_all, {...})` to ensure synchronization.

In practice

• Embed `shinyjs::runjs()` for custom JS scrolling.
• Use `which(input$TABLE_rows_all == r)` to find display index.
• Employ `observeEvent` for UI update synchronization.

Topics

• Shiny App Development
• DT Package
• JavaScript Scrolling
• Data Table Synchronization
• R Programming

Best for: Software Engineer, Data Scientist, Analytics Engineer

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Editorial summary, takeaway, and curation by AIssential. Original article published by OR in an OB World.