Recurrence Plot

The Recurrence Plot (RP) in GazePlotter reveals temporal self-similarity in a single participant’s fixation sequence. Each cell in the N×N matrix encodes whether two fixations (at indices i and j) landed in the same spatial region.

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• Metric Contract: This visualization computes recurrence patterns directly from the participant’s fixation sequence and does not consume metrics from the Metric Library.

Quantitative RQA Analysis: While this plot visualizes recurrences spatially, the quantitative metrics describing these recurrence structures (Recurrence Rate, Determinism, Laminarity) are managed separately in the Metric Library. See Recurrence Quantitative Analysis (RQA) Metrics for details on their mathematical definitions and ordinal windowing parameters.

Axis Convention

Interpretation of line structures in a recurrence plot is axis-convention-dependent. GazePlotter uses the following convention:

• Y-axis (vertical) — Fixation i, index increasing upward (fixation 1 at the bottom, fixation N at the top).
• X-axis (horizontal) — Fixation j, index increasing rightward (fixation 1 at the left, fixation N at the right).
• Main diagonal runs from bottom-left to top-right (i = j).
• Visual upper triangle (above diagonal): cells where i > j.
• Visual lower triangle (below diagonal): cells where i < j.

All directional terms in this document refer to this visual layout.

Configuration via Settings Pane

Clicking the Recurrence Plot card in the workspace selects the plot and opens its configuration options in the sidebar Settings Pane (or bottom sheet on mobile). The settings are organized into the following collapsible sections:

Stimulus

Choose the stimulus to analyze. Only fixations recorded for that stimulus are included.

• Edit stimulus library…: Opens the Stimuli Modification modal to manage stimulus files and dimensions.

Participant

Select which participant’s fixation sequence to analyze. The recurrence plot operates on a single participant at a time. The fixation index order follows the temporal order of recorded fixations for the selected stimulus.

• Edit participants…: Opens the Participant Modification modal to customize participant properties and metadata.

Method

Configure the criteria and rules used to decide whether two fixations are recurrent.

• Recurrence method: Choose the rule that determines when two fixations are counted as recurrent:
  • Fixed distance: Two fixations i and j are recurrent if their Euclidean distance on the stimulus plane is ≤ the specified radius.
  • Fixed grid: The stimulus plane is partitioned into a uniform grid. Two fixations are recurrent if they fall within the same grid cell.
  • AOI: Two fixations are recurrent if they share at least one Area of Interest. Fixations not assigned to any AOI are never recurrent with any other fixation under this criterion.
• Radius [px] (visible only in Fixed distance mode): Maximum screen-space distance (in pixels) between two fixation centroids for them to be counted as recurrent.
• Cells per axis (visible only in Fixed grid mode): Number of grid divisions along each axis (e.g. 10 creates a 10×10 grid).
• Duration weighting: When checked, each recurrent dot’s radius and opacity scale with the combined duration of the two fixations (t_i + t_j). Larger, more opaque dots indicate pairs of longer-duration fixations.
• Min line length: Minimum run length (in consecutive recurrent cells) required for a line structure to be recognized in highlight mode (from 2 to 20).

Visualisation

Configure highlights and masking options.

• Highlight: Emphasizes recurrent points that form qualifying line structures. Non-highlighted points are dimmed:
  • None: No highlighting. All recurrent points rendered at full opacity.
  • Diagonal lines: Highlights points belonging to diagonal line runs (parallel to the main diagonal) of length ≥ Min line length. Indicates periodic recurrence — the gaze returned to the same region after a consistent time lag.
  • Horizontal lines: Highlights horizontal line runs of length ≥ Min line length. In the visual lower triangle (i < j, fixed row i): fixation i recurs with many consecutive later fixations, indicating a laminar state anchored at time i.
  • Vertical lines: Highlights vertical line runs of length ≥ Min line length. In the visual lower triangle (i < j, fixed column j): many early fixations recur with fixation j, indicating a region revisited heavily before time j.
• Masking: Controls which cells of the N×N matrix are rendered:
  • None: All N×N cells rendered, including the main diagonal.
  • Diagonal: Main diagonal cells (i = j) are rendered as solid gray squares. All off-diagonal recurrent cells are rendered as dots (Default).
  • Diagonal + lower: The main diagonal and the entire visual lower triangle (i < j) are rendered as a solid gray region. Only the visual upper triangle (i > j) is plotted as recurrent dots.

Symmetry note: Because the recurrence matrix is symmetric (R[i,j] = R[j,i]), horizontal structures in the visual lower triangle are reflected as vertical structures in the visual upper triangle, and vice versa. The highlight is mirrored accordingly.

Time range [ms]

Filter the temporal range of fixations.

• Start: Limit the minimum time boundary (ms).
• End (0 = Auto): Limit the maximum time boundary (ms) or leave at 0 for automatic duration matching.

Areas of Interest

Filters which Areas of Interest (AOIs) are active when using the AOI recurrence method.

• Configure AOI Library…: Opens the AOI Modification modal to add, remove, rename, or color-code AOIs.

Export

Located at the bottom of the Settings Pane:

• Download plot…: Opens the export modal to download the plot.
  • File formats: PNG (transparent background) or JPG (white background).
  • Dimensions: Customizable width (height maintained as square).
  • Quality: Adjustable DPI setting.
  • Margins: Configurable margins.
  • Preview: Live render of the output before saving.

Interpretation

Pattern	What it suggests
Diagonal lines (parallel to main diagonal)	Periodic revisitation — the participant repeated a similar scanpath segment after a consistent time lag. Longer diagonal lines indicate more sustained repetition.
Anti-diagonal lines (perpendicular to main diagonal)	The fixation sequence was traversed in reverse order — the gaze retraced its earlier path backwards.
Horizontal lines	Fixation i recurred with many consecutive later fixations — the gaze was “trapped” in a region that was revisited repeatedly over an extended period.
Vertical lines	Many consecutive earlier fixations recurred with fixation j — a region that had been visited persistently was returned to at time j.
Recurrences clustered near the diagonal	Short-range temporal repetition — gaze returned quickly to the same regions.
Recurrences spread far from the diagonal	Long-range recurrence — the participant returned to the same regions after long intervals.
Visible block structure	Distinct fixation phases, each confined to a different spatial region. Block boundaries mark transitions between phases.

Axis convention reminder: All directional descriptions above assume GazePlotter’s convention: Fixation i on the y-axis increasing upward, Fixation j on the x-axis increasing rightward. The main diagonal runs bottom-left to top-right.