Signal Viewer

The central viewer displays synchronized multi-channel PSG signal and annotation data.

Top panel

The top panel displays:

• clock times in hourly intervals (24-hour format) across the top

• a representation of the hypnogram, when staging data are present: NREM, REM, and wake are blue, red, and green respectively

• a lower representation of the currently included (i.e. unmasked) epochs at the bottom

Pan/zoom navigation

You navigate across signals by clicking on this top panel. The white bar marks the interval shown in the lower panel. Cursor keys can also be used:

• left/right : move one epoch (30 seconds) backward or forward in time

• shift + left/right : move multiple epochs backward or forward

• up/down : zoom in/out to change the span of the lower panel; unless you've Rendered the data (see below), the maximum span is 30 seconds

• click-and-drag : if you've rendered the data, you can click and drag to select a larger time window; if you double-click within the selected region, it will return to a single-epoch view; you can also resize or drag the selected interval

Zoom and pan controls allow precise inspection of signal segments. For continuous signals, zooming out eventually switches to a min/max summary per screen pixel, and at broader spans Lunascope uses an interquartile-style summary to avoid visual saturation.

Measurement probe

In the main signal panel, press and hold the left mouse button to bring up a temporary measurement probe. This acts like a visual caliper: it shows the value at the current point, and while you keep dragging within the same channel it also reports the value difference and elapsed time between the start point and current point.

While the probe is active, Lunascope can also show extra overlays such as nearby annotations, peak markers, zero-crossings, simple window statistics, and optional time grid lines.

The probe shortcuts are shown in the on-screen legend while it is active. In practice, this means you can keep the basic caliper behavior simple, then toggle extra overlays only when you need them.

Rendering data

The main panel also includes controls for altering the view, including a Render button.

The viewer operates in two modes:

• On first attaching an EDF, Lunascope loads signals directly from the in-memory EDF as needed. Signals and annotations can be included or excluded through the Signals and Annotations docks. In this mode, no more than 30 seconds of signal data can be viewed at once, although annotation-only views are not subject to that limit.
• After pressing Render, Lunascope takes a snapshot of the currently selected signals and annotations and processes those data for more efficient viewing. Subsequent displays come from the rendered cache rather than the live in-memory record.

Rendering generates decimated, anti-aliased versions of the data and supports further downsampling, which makes it practical to view hours of data without plotting millions of sample points directly.

There are three main advantages to rendering signals:

• it allows for larger windows to be viewed efficiently

• it allows for better Y-axis scaling of signals (see below)

• it precomputes various summary statistics and other things that can enhance visualization (although these are not yet included in the alpha release of Lunascope)

Three things are worth keeping in mind when using rendering:

• Rendering speeds up later viewing, but the initial render can take time because the full dataset must be preprocessed, especially for large studies with many channels or high sampling rates.
• Rendering only includes the currently selected signals and annotations. If you add a new signal or annotation later, render again.
• If the underlying signal data change, for example through filtering, referencing, or rescaling in the console, the rendered view does not update automatically. The Render button turns orange after any Luna script to indicate that the rendered cache may be stale.

Y-scaling

After rendering, the button turns from white to green to indicate that display items are now drawn from the current snapshot. Rendering also allows different y-axis scaling modes:

• By default, unrendered signals autoscale within the current view window. As you scroll, the scale can change, and extreme values can flatten the rest of the trace.
• Empiric Y sets each track to the 10th and 90th percentile after rendering. This fixes the scale and usually makes amplitude changes easier to compare while scrolling, although extreme values can extend beyond the nominal track area.
• Clip Y prevents that overlap by clipping the signal to the top and bottom of each track.

Examples are these three views for the same interval and set of signals:

Default (autoscaling):

Empiric scaling:

Empiric scaling with clipping:

Other viewing options

Other viewing options include:

• show or hide labels for signals and annotations with Labels
• set fixed Y-axis minimum and maximum values with Fixed Y; this currently applies to all signals
• alter spacing and scaling for each signal track
• change the viewer color scheme from the top Palette menu

An advanced render-only feature is signal modulation (sigmod), which adds color-coded overlays to rendered traces based on derived signal properties.