Histogram
The SPC Histogram panel displays time series data as a histogram — a bar chart that shows how often values fall into specific ranges (called buckets). This is the foundation for all other features like control charts, bell curves, and the statistics table.
Bucket Settings
Configure how the histogram groups your data in Editor > Histogram:
| Option | Description |
|---|---|
| Bucket count | Approximate number of bars in the histogram. Default is 30. The actual count may differ slightly to produce clean bucket boundaries. |
| Bucket size | Fixed width for each bucket. When set, this overrides the bucket count. Leave on "Auto" to let the panel calculate an appropriate size. |
| Bucket offset | Shifts the bucket boundaries by a fixed amount. Useful when your data doesn't start at zero and you want buckets aligned to specific values. |
Combine Series
When you have multiple data series, the Combine series toggle merges them into a single histogram. This is useful when you want to see the overall distribution across all series rather than comparing them side by side.
When turned off (the default), each series gets its own set of histogram bars with a distinct color.
Feature Queries
If you have additional queries in your data source that provide reference values (like specification limits or targets) rather than histogram data, mark them as Feature Queries in Editor > Histogram > Feature Queries.
Feature queries are excluded from the histogram calculations. Their data is only used when you reference them in custom control lines (see Control Chart for details).
Appearance
You can customize the look of the histogram bars under field overrides or the defaults section:
| Option | Description |
|---|---|
| Line width | Border thickness of each bar (0-10) |
| Fill opacity | Transparency of the bar fill (0-100%) |
| Gradient mode | Apply a gradient effect to the bar fill |