Documentation Vision Library+ Documentation

Event Comparison Chart+

Event Comparison Chart+ lays the same attribute of many event frames, such as production batches, on one elapsed-time axis. You see at a glance which batch ran differently, how far it is from a golden batch, and which shift or asset it belongs to.

Overview

Event Comparison Chart+ with batch traces, a golden batch with its tolerance band and the batch table

Watch the demo

See Event Comparison Chart+ in a practical PI Vision workflow.

Open video in a new tab Browse the complete demo gallery

When to use it

Use this symbol when you need to:

  • Overlay the batches that an event frame search finds and compare their shape, not their clock times.
  • Compare batches that run for different lengths by aligning them on their start, their end or their relative progress.
  • Judge a batch against a golden batch and a tolerance band.
  • Explain differences by context, such as shift, asset or product, using color and table columns.
  • Read the value of every batch at the same point, and list the minimum, maximum and average per batch.

Choose Combo Chart+ to trend values over clock time. Choose Events Table+ to list event frames without plotting them.

Before you begin

  • The PI System has AF event frames with a template, for example Batch, whose attributes are numeric and have a PI Point reference.
  • Text or enumeration attributes, such as a shift, are used as category attributes. They color and describe batches and are not plotted.
  • Configure PI Web API for Vision Library+. See the installation guide.
  • You can read the event frames and their attributes in AF.

Add and set up the symbol

  1. In the PI Vision Events pane, search for the event frames to compare, for example Event Type Batch.
  2. Drag an attribute of one event frame onto the display and select Event Comparison Chart+. The symbol takes over the search of the Events pane.
  3. Set the display time range so that it contains the batches, for example 2026-04-20 to 2026-04-23.
  4. Right-click the symbol and select Events Search Criteria... to check the Time Range, Event Type and Event State. See Choose which batches to compare.
  5. Wait for the data. Each batch is drawn as one trace from its own start, and the table lists the batches.
Event Comparison Chart+ with six batches and the batch table

Common tasks

Choose which batches to compare

Use this first, because the chart is only as useful as the batches in it.

  1. Right-click the symbol and select Events Search Criteria....
  2. Keep Time Range on Timebar Duration (1) so the chart follows the display time range. Custom Time Range fixes it.
  3. Under Event Type and Attribute Value, select the event template, here Batch (2).
  4. Set Event State (3) and any other filter that makes the batches comparable, such as Asset Name.
  5. Select Apply (4). The chart reloads.
Events Search Criteria pane with Time Range, Event Type, Event State and Apply marked

The table lists every batch found. A batch is found when it was active in the time range, so a long batch that began earlier is included.

Align batches that run for different lengths

Use this when batches differ in duration and you want to compare how they develop.

  1. Right-click the symbol and select Configure Event Comparison Chart....
  2. Under Axes > Axis X, set Data Alignment (1) to Matched Start, Matched End or Normalized (0-100%).
Axis X group with Normalized (0-100%) selected

With Matched Start, every batch starts at 0s and the axis counts elapsed time, so you see how the start of each batch behaves. Matched End puts 0 at the end of each batch, for the run-in to completion. Normalized (0-100%) stretches every batch to the same width, so batches of 12 and 96 hours lie on top of each other:

Six batches aligned from 0% to 100% of their own duration

The tooltip still shows the real timestamp of each value.

Compare batches against a golden batch

Use a golden batch when one batch is your reference and you want to see whether the others stay close to it.

  1. In the table, select the star of the reference batch.
  2. The batch moves to Referenced Events. Its trace becomes a thick line, and a band surrounds it.
  3. Right-click the symbol and select Configure Event Comparison Chart....
  4. Under Events > Tolerance Band, check that Enabled is on.
  5. Set Type, Upper Limit and Lower Limit.
Table with the star of the golden batch marked, the golden line and the tolerance band marked
Tolerance Band group with Enabled, Type and Upper Limit marked

In the first image, (1) is the star, (2) the golden line and (3) the tolerance band. In the second, (1) is Enabled, (2) Type and (3) the limits. Batches inside the band follow the reference. Percent of Average sets the band as a percentage of the golden value at each point, Absolute Value as a fixed amount. Select several stars to build an average of the golden batches. Use the pin next to the star to keep any batch on the chart even when the search no longer finds it.

Color the batches by Shift

Use this when the question is why batches differ, and the answer may be in an attribute such as shift.

  1. In Attributes, select the attribute, here Shift, and make sure Role is Category.
  2. Under Events > Series, set Color By (1) to Shift.
  3. Under Trend Options > Legend, set Enabled to ON.
Series group with Color By set to Shift

Every shift gets one color, and the legend names the colors. Batches without a trace in the time range do not appear in the legend. Category Values in the table adds the same attributes as columns.

Batches colored by shift with a legend

Read batch statistics and hide batches in the table

Use this to compare batches by number, or to take a distracting batch off the chart.

  1. Right-click the symbol and select Configure Event Comparison Chart....
  2. Under Table, set Height (%) - 0 = Auto (1) to a larger value if the rows do not fit.
  3. Set Category Values (2) to ON to add the category attributes as columns.
  4. Set Plot Values (3) to ON, then switch on Min (4), Max and Average.
  5. Select the eye of a batch in the table to hide its trace. Select it again to show it.
Table group with Height, Category Values, Plot Values and Min marked

In the table, (1) marks the Min, Max and Avg columns of the plotted attribute, (2) the eye of the hidden batch and (3) the category values, here the shift. A batch without data in its window shows No Data. The hidden batch keeps its row and loses its trace.

Table with Min, Max, Avg and Shift columns and one batch hidden

Read every batch at the same point in time

Use rulers to answer "what did each batch do 20 hours in?".

  1. Click the plot where you want ruler A (1).
  2. Click again for ruler B.
  3. Read the values of every batch at each ruler (2).
  4. To remove the rulers, select Clear rulers (3) in the toolbar. Turn the toolbar on first with Trend Options > Toolbar > Show Toolbar.
Two rulers with value labels for every batch and the toolbar

The ruler label shows the elapsed time of the ruler. Rulers are not saved.

Use the symbol

Event Comparison Chart+ with six numbered callouts
What it shows
(1)The trace of one batch. Its color follows Color By.
(2)The golden batch as a thick line.
(3)The tolerance band around the golden batch.
(4)The elapsed-time axis. It starts at 0s for Matched Start, counts back to 0 for Matched End and runs from 0% to 100% for Normalized.
(5)The zoom slider. Drag its handles to zoom.
(6)The batch table, with the eye, the pin and the star of each batch.

Interactions

  • Hover the plot to see a tooltip with the elapsed time, and for each batch the attribute, its value and the real timestamp of the value.
  • Zoom with the mouse wheel or the zoom slider. A drag pans the plot or draws a zoom box, as set in Drag mode. The toolbar offers Pan, Box zoom, Zoom In, Zoom Out, Reset Zoom, Clear rulers, Fullscreen and Download. Download exports PNG, SVG, PDF, CSV, JSON or XLSX.
  • Click the plot to place ruler A, then ruler B. With both rulers placed, the plot outside them is shaded, and an A-B arrow at the plot edge points to rulers outside the visible range. The rulers are shared with other Event Comparison Chart+ symbols that use the same alignment.
  • In the table, the eye hides or shows a batch, the pin keeps it as a reference, and the star makes it golden. The details button opens the event frame details, where Edit changes the event frame in AF. Apply to Display Time sets the display time range to the batch.
  • A filter symbol such as Event Filter+ on the display narrows the batches. A badge, here 12 of 29 events, tells how many are left. See Filtering dashboards.

Selecting, hiding, pinning and rulers do not change the event frames. Pins and golden batches belong to the display and are saved when you save it. Batches that are still running grow with each refresh and are shown with the live trace style when Highlight Active Events is on.

Configure the symbol

The pane has the sections Trend Options, Events, Interactivity, Table, Axes and Attributes, then the common sections such as Numbers and Web API. The event search is set with Events Search Criteria... in the context menu.

Trend Options

SettingWhat it does
Title, Sub TitleShow a title and a subtitle, each with its own ON/OFF and text.
StyleTheme, Surface, Container Style, Apply to all symbols, Foreground, Background and Font Size. Foreground and background are available when the theme is Custom Theme.
LegendEnabled shows the legend, with Position, Placement, Alignment, Size and Color (MARKER or TEXT). It names the groups from Color By.
GridShow, Lines (None, Horizontal, Vertical, Both), Bands and Border (AXES, FRAME, NONE).
TooltipShow, Pointer (NONE, ARGUMENT, CROSS) and Category, which adds the category values to each row. Tooltip Mode (Current Chart or All Charts) is available with separate scales.
ToolbarShow Toolbar shows the button strip. Reveal: ON HOVER shows it while the pointer is on the chart, ALWAYS keeps it visible and makes the plot a little shorter. Touch devices always show it.

Events

SettingWhat it does
Context (Offsets)Pre-Event Offset and Post-Event Offset load extra data before the start and after the end of each batch, in Seconds, Minutes, Hours or Days. Use them for lead-up and recovery. Large offsets crowd the chart.
SeriesHighlight Active Events styles running batches differently: Live Trace Styling and Historical Trace Styling (Line Width, Opacity, Line Style). Color By picks an event property or category attribute. See Color the batches by Shift. Coloring is AUTO or CUSTOM, with a Palette of Classic or Soft.
Tolerance BandCenter line styles the golden line. Enabled, Type (Percent of Average, Absolute Value or Sample Standard Deviation), Upper Limit, Lower Limit, Color, Opacity and Boundary Lines style the band. Sample Standard Deviation needs at least two golden batches running at the same point. See Compare batches against a golden batch.
Child EventsShow draws the child event frames of each batch as bands. Color is Series (the batch color) or Custom, with a Custom Color.

Interactivity

SettingWhat it does
GeneralEnable Zoom turns the wheel zoom, the zoom box and the zoom buttons on or off. Drag mode (PAN or BOX ZOOM) is the drag action when the display opens. Show Scrollbar shows the zoom slider. Synchronize Hover and Ruler share the cursor and rulers with other Event Comparison Chart+ symbols that use the same alignment.
FilteringIgnore Master keeps the chart from reacting to Master filters. Linked Inputs map named filter channels to event properties. The chart receives filters and does not publish any. Pinned and golden batches stay on the chart whatever the filters say. Filter Indicator is Compact (default: the filter icon, expanded to the full chip while you hover over the chart or tap the icon), Full (always the full chip) or Hidden (no chip). Waiting for filter shows in every mode.

Table

SettingWhat it does
Enabled, Height (%) - 0 = AutoShow the table. A height of 0 sizes it to its rows. See Read batch statistics and hide batches in the table.
Category ValuesAdds a column for each category attribute.
Plot ValuesAdds Min, Max, Average, Time at Min and Time at Max of each plotted attribute. Average is on by default.
ColumnsAsset, Status, Start Time, End Time, Duration and Annotations show or hide a column. Shift adds a time-shift field to each row, for trying a batch a few minutes earlier or later, such as 5m or 1h. The shift is not saved and does not change the event frame.

Axes

SettingWhat it does
Axis XData Alignment (Matched Start, Matched End, Normalized (0-100%)). Show, Position (Bottom or Top), Title and its Text. See Align batches that run for different lengths.
Axis YChoose Single, Multiple, Separate or Custom scales. Single shares one axis, Multiple draws one axis per attribute in one plot, Separate stacks one panel per attribute, with Chart Height AUTO or FIXED. Label Position is Inside or Outside. Use a shared scale only when the attributes have the same unit.

Attributes

SettingWhat it does
Attribute listThe attributes of the symbol. The buttons below the list change the order, which sets the draw order, the panel order and the table order.
Custom labelReplaces the attribute name in the legend, tooltip and table.
RoleTRACE plots the attribute. CATEGORY uses it for color, tooltip and table columns. Use few traces and many categories.
Series Type, StepLINE, AREA or SCATTER. Step holds each value until the next one, for digital or phase attributes.
Value ScaleAvailable with Multiple, Separate and Custom scales: Show, Position (LEFT, RIGHT), Invert Scale, Transform (LINEAR, LOGARITHMIC), Scale Range (AUTO, DATABASE, CUSTOM), Title and Ticks. DATABASE uses the AF limits of the attribute.
Configure Multi-State...In the context menu. Draws state or limit lines for the selected trace attribute.

Troubleshooting and limitations

SymptomCauseWhat to do
The chart and the table are empty.The search finds no batch, because the Event Type, Event State or time range do not match.Right-click the symbol, select Events Search Criteria..., widen the Time Range and select Apply.
A batch is in the table but has no trace.The batch has no values for the plotted attribute in its window, and the table shows No Data.Check the attribute in AF, or add a Pre-Event Offset or Post-Event Offset.
The golden batch has no line or band.The golden batch has no values, or Tolerance Band > Enabled is off.Choose another golden batch, and check Enabled.
A batch stays on the chart after the search changed.The batch is pinned or golden, and these stay whatever the search finds.Select its pin or star again.
Colors by Color By change when the search changes.Coloring is AUTO, so colors follow the groups found.Set Coloring to CUSTOM and choose a color for each value.

Limitation: Zooming applies to the elapsed-time axis only. There is no Apply to Display Time option for the zoom, because the axis does not show clock time. Use the clock button in the table for a batch.

Limitation: Large batch counts and many traces slow the browser. Narrow the search, or hide batches in the table.