Query & Analysis Tools¶
The query rectangle lets you select a region of your plot and instantly see statistics about the data inside it — min, max, mean, frequency content, rise time, and more.
Creating a Query Rectangle¶
Ctrl + drag in any subplot to draw a rectangular selection. A green overlay shows the selected area. When you release the mouse, a tooltip appears with statistics for every visible series inside the rectangle.
You can also middle-click + drag as an alternative to Ctrl + drag.
Adjusting the Rectangle¶
After creation, the rectangle has interactive handles:
- Corners — drag to resize in both dimensions
- Edges — drag to resize in one dimension
- Interior — drag to move the whole rectangle
Statistics recalculate each time you release after an adjustment. Creating a new rectangle replaces the previous one (one per subplot).
Statistics¶
Results appear in a tooltip anchored to the rectangle corner. Each visible series inside the rectangle gets its own section.
Basic Statistics¶
| Statistic | Description | Default |
|---|---|---|
| Mean | Average value | On |
| Delta | Peak-to-peak (max minus min) | On |
| Min | Minimum value | Off |
| Max | Maximum value | Off |
| Std | Standard deviation | Off |
| Count | Number of data points | Off |
Window Measurements¶
| Statistic | Description | Default |
|---|---|---|
| Window Width | Time span of the selected region (seconds) | On |
| Window Frequency | 1 / window width (Hz) | Off |
Signal Analysis¶
| Statistic | Description | Default |
|---|---|---|
| Ramp Rate | Rate of change from first to last point in the region (units/s) | Off |
| RMS | Root mean square value | Off |
| Dominant Frequency | Peak frequency via FFT with Hann windowing and parabolic interpolation | Off |
Power Systems Metrics (NER)¶
These are specialized calculations for power systems analysis. Two NER standard variants are available — NER 233 (legacy, uses maximum change) and NER 234+ (current, uses sustained/mean change):
| Statistic | Description | Default |
|---|---|---|
| Rise Time (NER 233) | Time for 10%-90% of maximum change | Off |
| Rise Time (NER 234+) | Time for 10%-90% of sustained change | Off |
| Recovery Time | Time to reach 95% of initial value after a disturbance | Off |
| Settling Time (NER 233) | Time to stay within 10% tolerance band (see note below) | Off |
| Settling Time (NER 234+) | Time to stay within 10% tolerance of sustained change | Off |
| Damping Ratio | Oscillation damping via matrix pencil method | Off |
NER 233 vs NER 234+
NER 234+ always measures against the sustained change (final value minus initial value) for both rise time and settling time.
NER 233 uses the maximum excursion (including overshoot) for rise time. For settling time, it picks whichever is larger between max excursion and sustained change — so if there's significant overshoot, the tolerance band gets wider.
Configuring Which Statistics to Show¶
Open Settings and look for the query options. Each statistic can be toggled on or off independently. Only enabled statistics appear in the results tooltip.
How Results are Displayed¶
When you release the mouse after creating or adjusting a rectangle:
- All visible series inside the rectangle are identified
- Data is filtered to the rectangle's X (time) and Y (value) bounds
- Each enabled statistic is calculated per series
- A green tooltip appears at the corner of the rectangle showing all results, grouped by series name
The tooltip is automatically replaced when you adjust the rectangle or create a new one.
Multi-Series Analysis¶
When multiple series fall inside the rectangle, each one is analysed independently. Results are grouped by series name so you can compare values side by side — useful for checking how different signals behave over the same time window.
Working with Transformed Data¶
Query rectangles work correctly with transformed data. If you've applied scaling or offsets to a series (via templates or the legend sliders), the query coordinates are automatically inverse-transformed to match the original data before filtering. This means the statistics reflect the transformed values you see on screen.
Tips¶
- Quick measurement: Ctrl + drag a narrow rectangle across a signal to get its value at a specific time — check the mean. This saves reading off the y-axis.
- Frequency measurement: Draw a rectangle spanning exactly one cycle of an oscillation. The window frequency tells you the signal frequency directly without needing FFT.
- Comparing responses: With multiple files plotted on the same subplot, a single query rectangle lets you compare statistics across all of them at once.
- Rise/settling time: For meaningful NER results, draw the rectangle from just before the disturbance to well after settling. The calculations need at least 10 data points.