eventmarker

Interactive event marker manager for MATLAB plots. Lets a user mark, label, drag, resize, save, and reload events on top of any 2-D plot — with full support for both numeric and datetime x-axes.

Designed for sleep / time-series work where a scorer is reviewing a spectrogram or a waveform and wants to flag instants (onsets, artifacts) or intervals (REM epochs, arousals, artifact regions) and later consume them programmatically.

Components

Class	Role
EventMarker	Main orchestrator. Attaches to an axes, owns the event list, handles mouse/keyboard, manages selection.
EventObject	Value class describing either an event type (name, ID, region-vs-point, constrain flag) or a placed instance (also carries graphics handles + unique event_ID).
DateTimeLine	Draggable vertical line primitive used for point events. Works with both numeric and datetime axes.
DateTimeRectangle	Draggable, resizable rectangle primitive used for region events. Works with both numeric and datetime axes.

Entry point

marker = EventMarker(ax, xbounds, ybounds, event_types, event_list, line_colors, font_size)

All arguments optional — ax defaults to gca, bounds default to the current axis limits, colors to the axes ColorOrder, font size to 12.

Argument	Meaning
ax	axes handle to attach to
xbounds	[xmin xmax] limits within which markers may be placed
ybounds	[ymin ymax] limits for marker placement
event_types	array of EventObjects describing the palette (REM, Spindle, Artifact, …)
event_list	optional pre-existing events to reload (e.g. from a prior save)
line_colors	Nx3 color per type
font_size	label font size

Event types vs. events

An EventObject plays two roles:

1. Type definition — created once per marker category. Carries name, type_ID, region (true = rectangle, false = line), and constrain (for regions, whether they span the full y-axis vertically or can be drawn at arbitrary height).
2. Placed instance — created each time the user marks an event. Shares the type's fields plus a unique event_ID (random UUID-like int) and the live graphics handles (obj_handle, label_handle).

Build a palette once, hand it to EventMarker, and it takes care of instance creation from there.

Interaction model

• Place — press a hotkey assigned to a type, then click once (point) or click twice (region start/end).
• Select/edit — double-click an existing event to enter edit mode: DateTimeLine / DateTimeRectangle becomes interactive (drag to move, drag edges to resize).
• Delete — select an event then press Backspace/Delete.
• Save/Load — via menu or Ctrl+S / Ctrl+L. Persists the event_list as .mat for later reload.

The actual hotkey mapping (1/2/3/4/Space) lives in the viewer script, not in EventMarker — keeping the marker class hotkey-agnostic so each viewer can define its own bindings.

DateTime support

DateTimeLine and DateTimeRectangle both detect whether the parent axes uses datetime x-values and transform interactively between screen pixels and datetime values. This is the key value-add over a plain draggable ROI: datetime axes aren't natively editable by MATLAB's drawline / drawrectangle.

Demo

cd eventmarker/example_viewer
basic_viewer

The demo creates a two-panel figure (pseudo-spectrogram on top, time-series below), attaches an EventMarker to the top axes, and wires up four event types plus save/load:

Hotkey	Action
1	Mark REM region (full-height, constrained)
2	Mark "Eyes Closed" point
3	Mark Alpha region (unconstrained height)
4	Mark Arousal point
Space	Add a free-text annotation
Backspace / Delete	Delete selected event
Ctrl+S	Save events
Ctrl+L	Load events
Double-click event	Enter edit mode

Typical viewer-script skeleton

% 1. Build your figure + axes
f  = figure;
ax = axes(f);
imagesc(t, f_vec, S); axis xy

% 2. Define event-type palette
types = [ ...
    EventObject('REM',         1, true,  true ); ...   % region, full-height
    EventObject('EyesClosed',  2, false, false); ...   % point
    EventObject('Alpha',       3, true,  false); ...   % region, free-height
    EventObject('Arousal',     4, false, false) ];     % point

colors = lines(numel(types));

% 3. Attach marker
marker = EventMarker(ax, [t(1) t(end)], ylim(ax), types, [], colors, 12);

% 4. Install a KeyPressFcn that calls marker.addEvent(type_ID) for your hotkeys
f.KeyPressFcn = @(s,e) my_hotkey_handler(marker, e);

% 5. After scoring, read back:
events = marker.event_list;   % EventObject array

Files in this directory

• EventMarker.m — orchestrator class (entry point)
• EventObject.m — type definition + placed-instance record
• DateTimeLine.m — draggable line primitive (datetime-aware)
• DateTimeRectangle.m — draggable/resizable rectangle primitive (datetime-aware)
• example_viewer/basic_viewer.m — runnable demo
• README.md — this file

Dependencies

Base MATLAB only. No toolboxes required. basic_viewer.m uses figdesign and suptitle from utils/ for layout but the core classes do not.