Gantt Chart

Overview

The Gantt Chart custom visualization shows tasks on a timeline using Start Date and End Date. Each task appears as a horizontal bar. If your data contains multiple rows with the same task name, the visualization can merge them into one bar that spans the earliest start and latest end date. Tasks can be grouped to add alternating background bands, which makes large charts easier to scan. Optional numeric measures appear in tooltips and (if configured) can also appear in task labels.

You can use the Gantt Chart to:

Plan project or program schedules using task start and end dates.
Create release or sprint plans with milestones and phases.
Review portfolio timelines by grouping tasks by workstream, owner, or department.

Gantt Chart

How the Visualization Displays Data

Bars and milestones:
- If a task has a valid Start Date and End Date, it appears as a bar from start to end.
- If End Date is the same as Start Date (or earlier), the task appears as a milestone (diamond).
Grouping
- Tasks are grouped by a Group field.
- Each group appears in its own horizontal band with alternating background shading and separators.
Labels
- Each bar shows a task label near the bar.
- Labels use a compact font to reduce overlap
Tooltips
- When you hover over a bar or milestone, the tooltip shows: Group, Task, Start Date, End Date, Reference Date, Duration (days), and any numeric measure provided.
- Numeric values are formatted with thousands separators and two decimal places.
Reference date line
- Each task can display a vertical line at its Reference Date to indicate a key checkpoint (for example, a data as-of date).
Time axes
- The chart shows four synchronized axes at the top: Day Month Quarter Year: Days, Month, Quarter, and Year.
- Tick density automatically adjusts to the visible date range and available width.
Duplicate task handling (consolidation)
- If multiple rows have the same Task Name (and the same Color, if provided), the visualization merges them into one task: Start Date = earliest Start Date, End Date = latest End Date, Reference Date = latest Reference Date, Duration = recalculated from the merged start and end dates, Measures (if present) = summed across the merged rows.

Data Requirements

Provide the following fields in your dataset and assign them to the shelves indicated. The visualization expects the required fields to render.

Required fields

Field

Shelf

Start Date

Row

End Date

Row

Reference Date

Row

Task Name

Row

Group

Category

Optional fields

Color (Color): A categorical field used to color tasks. If you use Color, tasks are merged only when Task Name and Color both match.
Measures (Values): 0–5 numeric measures. These appear in tooltips and can be included in the label. When tasks are merged, measures are summed.

Data Type and format notes

Use OAC Date or Date-Time types for Start Date, End Date, and Reference Date.
Make sure date values are valid and not empty.
Use text fields for Task Name and Group.
Measures must be numeric.

Configurable Properties

Axis font size

Location: Visualization Properties → General → Axis Font Size.
Purpose: Changes the font size of the timeline axes for readability.
Input: A small positive number (pixels), for example: 6, 8,10

Limits, Assumptions, and Constraints

Data Volume

Supports up to approximately 10,000 rows and 5,000 columns (plugin configuration limit).
Supports up to five measures.

Shelf minimums

Row: Start Date, End Date, Reference Date, Task Name
Category: Group
Color: Optional (one categorical field)

Date validity

Missing or invalid dates can prevent the chart from determining a time range and can result in a blank or incomplete chart.

Consolidation rules

Tasks are merged based on Task Name and (if supplied) Color.
Group is taken from the first occurrence.
Measures are summed when tasks are merged.

Layout

The chart uses the available canvas size.
With many tasks, labels might overlap or truncate. Consider filtering, grouping, or resizing the canvas.

Interactivity

Marking/selection and embedding are not supported by this plugin.

Building the Chart in OAC

Add the visualization to your canvas.
Assign fields:
- Row: Start Date, End Date, Reference Date, Task Name
- Category: Group
- Color (optional): a categorical field
- Values (optional): up to 5 numeric measures
(Optional) Set Axis Font Size in the properties.
Resize the canvas or filter data to improve readability.

Troubleshooting

Issue	Likely cause	What to check / how to fix
Chart does not render or appears empty	Required fields are missing or assigned to the wrong shelves. Invalid, missing, or blank date values prevent the chart from determining a time range	Confirm these assignments: Row: Start Date, End Date, Reference Date, Task Name Category: Group Verify Start Date and End Date contain valid dates in your dataset. Make sure the visualization can determine at least one valid date range.
Milestones shown unexpectedly	End Date is the same as Start Date, or earlier	Check the task’s Start Date and End Date values. If they are equal (or End Date is earlier), the visualization renders a milestone (diamond).
Unexpected merging of tasks	Duplicate consolidation is enabled by design for matching tasks	If multiple rows share the same Task Name (and the same Color, if used), they are merged. Use more specific Task Name values, or adjust Color to prevent unintended merges.
Colors not applied	No field is assigned to the Color shelf	Add a categorical field to Color. If Color is not provided, default colors are used.
Axis labels too small or overlapping	Axis font size is too small for the canvas size and date density	Update Axis Font Size (Visualization Properties → General). Also try resizing the canvas or filtering the date range.
Measures not visible in tooltip	Measures are not assigned to Values Measure values are blank or non-numeric	Assign your numeric fields to Values (up to five measures). Confirm the measures are numeric and populated. Blanks and non-numeric values are ignored.