Histogram+

Overview

Histogram+ groups numeric values into bins to show their frequency distribution over a selected period.

When to use it

Use this symbol when you need to:

• Review the spread and most common range of a process value.
• Compare distributions across several numeric data sources.

Before you begin

• Prepare numeric PI Points or AF attributes with recorded values in the selected range.
• Choose a bin count that is meaningful for the sample size.

Add and set up the symbol

1. Select the symbol in the PI Vision symbol gallery.
2. Add the required data sources or asset context to the display.
3. Right-click the symbol and open its configuration pane.
4. Configure the minimum data, range, and display settings for a useful result.
5. Confirm that the symbol shows the expected data.

Use the symbol

Hover over a bar to inspect its range and count. Use the time bar to compare distributions for different periods.

Time bar

The Time Bar lets you control the histogram's time range independently of the display's global time setting.

The time bar lets you quickly shift or resize the active time range without affecting the rest of the display. The following options are available:

• Enabled: Turns the time bar on or off.
• Ignore Display Time: When enabled, the symbol maintains its own time range and does not respond to global display time changes. This setting can also be toggled using the lock icon in the time bar toolbar.
• Duration: Defines preset time range options (e.g., 1h, 8h, 24h) that appear in the dropdown between the navigation arrows.
• Style: Sets the text color, background color, border color, and font size of the time bar.

Configure the symbol

Overview and behavior

The Histogram+ visualizes the distribution of quantitative data by grouping values into bins and displaying how frequently each range occurs. It supports statistical overlays - bell curve, mean, and standard deviation lines - and flexible axis configuration to suit a wide range of process analysis needs.

Basic configuration

Use the Configuration pane to customize the Histogram+ symbol. Options cover the chart title, visual styling, bar appearance, axis ranges, statistical overlays, and data retrieval behavior.

General

Histogram supports two different modes: Histogram and Pie

• Histogram: Will show a regular histogram. If histogram is enabled, you can also enable Stacking here if the symbol has multiple data sources
• Pie: Will show the individual buckets represented as a pie chart

Title

• Show: Toggles the chart title on or off.
• Title: The text displayed as the chart heading.
• Units: When enabled, appends the data source unit of measure to the title.
• Statistics: When enabled, appends the calculated mean and standard deviation values to the chart title.

Style

Controls the overall appearance

• Foreground: Sets the color of chart text and labels.
• Background: Sets the background fill color of the chart area.
• Font Size: Sets the base font size for all chart text.
• Opacity: The opacity of the bars
• Stroke: Colored border around the bars
• Grid: Controls the color and style of grid lines and axis lines.

Data Labels

Enable / Disable data labels

Legend

Configure Legend visibility and position

Axis X

The Axis X section controls the number of histogram bars and the scale range displayed on the horizontal axis. The following scale range modes are available:

• Database Settings: The axis min and max values are read from the PI point's Span and Zero attributes.
• Actual Data Range: The chart automatically fits the min and max values to the range present in the retrieved data.
• Custom Settings: Lets you specify fixed min and max values for the horizontal axis.

Finally you can configure the Tick Labels to show / hide and also change the tick interval from Auto to Custom.

Axis Y

The Axis Y section controls the scale of the vertical (frequency) axis. Two options are available:

• Actual Data Range: The chart automatically scales the Y axis to fit the frequency counts in the data.
• Custom Settings: Lets you specify fixed min and max values for the frequency axis.
• Labels: Toggles the display of numeric tick labels on the Y axis.

Data source options

These options are generally available for all data sources.

• Label: Change the displayed label of the data source
• Color: Color of the displayed bar

The Statistics section lets you overlay additional analytical markers on the histogram:

• Bell Curve: Overlays a Gaussian normal distribution curve on the histogram. You can also configure the color.
• Mean: Draws a vertical line at the mean value of the data.
• Standard Deviations: Draws vertical lines at 1, 2, or 3 standard deviations from the mean.
• Quantiles

You can add any number of quantile markers to the chart. Each quantile is defined by a percentage threshold - the chart draws a vertical line at the point where that percentage of values falls below (or above) it:

Data retrieval

Select the data retrieval method for the histogram. Recorded mode uses all stored data points; Interpolated mode uses only interpolated values at regular intervals.

When Recorded mode is selected, you can also configure a Calculation Basis. Event Weighted counts the number of discrete data points in each bin. Time Weighted weighs each bin by the duration the value was active rather than by event count.

Data export

When exporting, you can export the calculated histogram data shown in the chart, or select the Raw Data checkbox to download the underlying time series values used for the calculation.

Troubleshooting and limitations

• Check: If the histogram is empty, check the time range, retrieval mode, and whether the source contains numeric values.
• Check: Too many bins for a small sample can produce a sparse or misleading distribution.