# Vector migration files¶

Vector migration files describe the rate of migration of vectors out of a geographic node analogously to human migration (see Migration files for more information), although vector migration does not support gender and age parameters. Vector migration is one way, such that each trip made by a vector is independent of previous trips made by the vector. The rates in the file are used to control whether or not a vector will migrate: the rate specified is used to get a “time to leave on trip” value from an exponential distribution. If the value is less than one day, then the vector will migrate.

In order to use a vector migration file, the configuration parameter Vector_Sampling_Type must be set to either TRACK_ALL or SAMPLE_IND_VECTORS. If default geography is used (the configuration parameter Enable_Demographics_Builtin is set to 1, and Default_Geography_Initial_Node_Population and Default_Geography_Torus_Size are configured), vectors can only migrate (or not) using Enable_Vector_Migration, and vector migration files are not used.

Vectors can migrate regionally or locally, and there are multiple modifiers available to influence migration to particular nodes over others. See Configuration parameters for more information on the parameters governing vector migration.

The metadata file is a JSON-formatted file that includes a metadata section and a node offsets section. The Metadata section contains a JSON object with parameters, some of which are strictly informational and some of which are used by Eradication.exe. However, the informational ones may still be important to understand the provenance and meaning of the data.

### Parameters¶

The following parameters can be included in the vector migration metadata file:

Parameter

Data type

Description

Author

string

The author of the file.

DatavalueCount

integer

(Used by EMOD.) The number of outbound data values per node (max 100). The number must be the same across every node in the binary file.

DateCreated

string

The day the file was created.

IdReference

string

(Used by EMOD.) A unique, user-selected string that indicates the method used by EMOD for generating NodeID values in the input files. For more information, see Input files.

NodeCount

integer

(Used by EMOD.) The number of nodes to expect in this file.

NodeOffsets

string

(Used by EMOD.) A string that is NodeCount $$\times$$ 16 characters long. For each node, the first 8 characters are the origin NodeID in hexadecimal. The second 8 characters are the byte offset in hex to the location in the binary file where the destination NodeIDs and migration rates appear.

Tool

string

The script used to create the file.

### Example¶

{