Triggers

This demo shows how to inspect trigger (event marker) data and search for trigger sequences in EEG recordings.

Why Triggers?

Triggers mark experimental events (stimulus onsets, responses, conditions) in the continuous EEG recording. Before epoching, you need to verify that triggers are present, correctly coded, and occur at the expected frequencies.

Key Functions

Function	Purpose
trigger_count	Count occurrences of each trigger value
search_sequence	Find indices where trigger patterns occur
plot_trigger_overview	Visualise trigger distribution
plot_trigger_timing	Visualise trigger timing

Sequence Search Features

• Single values: find all onsets of trigger 1

• Multi-trigger sequences: find [1, 2] (cue followed by target)

• Wildcards: :any matches any trigger between specific values

• Ranges: 1:5 matches triggers 1 through 5

• Multiple sequences (OR logic): [[1, 2], [3, 4]] finds either sequence

Workflow Summary

Trigger Counting

• View raw and cleaned trigger counts in a formatted table

Sequence Searching

• Find single triggers, multi-trigger sequences, and patterns with wildcards

Visualisation

• Plot trigger timing and distribution

Code Examples

Show Code

# Demo: Triggers
# Shows how to inspect, count, and search for trigger sequences in EEG data.

using EegFun
# Note: EegFun.example_path() resolves bundled example data paths.
# When using your own data, simply pass the file path directly, e.g.:
# dat = EegFun.read_raw_data("/path/to/your/data.bdf")

#######################################################################
# LOAD DATA
#######################################################################

dat = EegFun.read_raw_data(EegFun.example_path("data/bdf/example1.bdf"))
layout = EegFun.read_layout(EegFun.example_path("layouts/biosemi/biosemi72.csv"))
EegFun.polar_to_cartesian_xy!(layout)
dat = EegFun.create_eegfun_data(dat, layout)


#######################################################################
# TRIGGER OVERVIEW
#######################################################################

# Count how often each trigger occurs (raw and cleaned)
trigger_info = EegFun.trigger_count(dat)

# View the trigger table
trigger_info

# Access the underlying DataFrame
trigger_info.data


#######################################################################
# SEARCH FOR TRIGGER SEQUENCES
#######################################################################

# Find all onsets of trigger value 1
idx = EegFun.search_sequence(dat.data.trigger, 1)

# Find a two-trigger sequence (e.g., warning cue followed by target)
idx = EegFun.search_sequence(dat.data.trigger, [1, 2])

# Find a sequence while ignoring zeros between triggers
idx = EegFun.search_sequence(dat.data.trigger, [1, 2], ignore_values = [0])


#######################################################################
# WILDCARDS AND RANGES
#######################################################################

# Use :any wildcard to match any trigger between two specific triggers
idx = EegFun.search_sequence(dat.data.trigger, [1, :any, 2])

# Use ranges to match a set of trigger values
idx = EegFun.search_sequence(dat.data.trigger, [1:5])     # triggers 1 through 5
idx = EegFun.search_sequence(dat.data.trigger, [1:3, 10:12])  # multiple ranges


#######################################################################
# MULTIPLE SEQUENCES (OR LOGIC)
#######################################################################

# Find onsets where any of several sequences occurs
idx = EegFun.search_sequence(dat.data.trigger, [[1, 2], [3, 4]])


#######################################################################
# VISUALIZE TRIGGERS
#######################################################################

# Plot trigger timing overview
EegFun.plot_trigger_overview(dat)
EegFun.plot_trigger_timing(dat)

See Also

• API Reference