bibliometrix (version 5.2.0)

assignEvolutionColors: Assign Colors to Thematic Evolution Nodes Based on Lineages

Description

This function assigns colors to nodes in a thematic evolution analysis based on their lineages across time periods. Nodes connected by strong edges (above a threshold) receive the same color to visualize thematic continuity. Nodes with the same name across periods that are not strongly connected to other nodes are also colored identically.

Usage

assignEvolutionColors(
  nexus,
  threshold = 0.5,
  palette = NULL,
  use_measure = "weighted"
)

Value

Returns the modified nexus object with updated colors:

• Nodes$color: updated with lineage-based colors

• Edges$color: edges connecting same-colored nodes receive the node color, others are grey

• TM: thematic maps updated with new cluster colors

Arguments

nexus

A list object returned by thematicEvolution containing:

• Nodes: data frame with node information (name, group, id, sum, freq, etc.)

• Edges: data frame with edge information (from, to, weight measures)

• TM: list of thematic maps for each period

threshold

Numeric. The minimum weight value for an edge to be considered a "strong connection" (default: 0.5). Edges with weights >= threshold will propagate the same color to connected nodes across periods.

palette

Character vector. Optional custom color palette as hex codes. If NULL, uses a default palette of 50+ distinct colors. Colors are assigned sequentially without reuse.

use_measure

Character. The measure to use for determining edge strength. Can be one of:

• "inclusion": uses the Inclusion measure (column 3 of Edges)

• "stability": uses the Stability measure (column 5 of Edges)

• "weighted": uses the weighted Inclusion measure (column 4 of Edges)

Default is "inclusion".

Details

The function uses a multi-phase algorithm:

1. Phase 1: Identifies lineages by following strong connections (weight >= threshold) from the first period forward. When a node has multiple strong connections, the strongest one determines the lineage.

2. Phase 1.5: Assigns the same lineage to nodes with identical names across periods if they are not already part of different strong connections.

3. Phase 2: Assigns unique colors from the palette to each identified lineage.

4. Phase 3: Assigns unique colors to isolated nodes (those without any lineage).

5. Phase 4: Colors edges based on their connected nodes - same color if both nodes share a color, grey otherwise.

6. Final: Updates thematic maps with the new color scheme.

Each lineage receives a unique color from the palette. No color is reused across different lineages, ensuring clear visual distinction between independent thematic streams.

See Also

thematicEvolution to perform thematic evolution analysis.

plotThematicEvolution to visualize the colored evolution.

Examples

if (FALSE) {
data(scientometrics, package = "bibliometrixData")
years <- c(2000, 2010)

nexus <- thematicEvolution(scientometrics, field = "ID",
                            years = years, n = 100, minFreq = 2)


# Use custom threshold and measure
nexus <- assignEvolutionColors(nexus, threshold = 0.6, use_measure = "weighted")

}