# BIASVAL

The `BIASVAL` field specifier (case sensitive) allows you to bias the score of result documents by a specified percentage, based on whether they include a specific value in the specified field.

NOTE: You can only use `BIASVAL` when the field is configured as:

- `MatchType`

- `ParametricType`, when the `ParametricNumericMapping` configuration parameter is set to `True`.

## Format

    FieldText=BIASVAL{fieldValue,percentBoost}:fieldName

`fieldValue` | The value that the specified field must contain to increase or decrease the weight by the `percentBoost`.
`percentBoost` | A percentage in the range -100 to 100. The percentage (positive or negative) by which to boost the relevance of documents that have the value `fieldValue` in the field `fieldName`. (The boosted relevance score cannot be greater than 100% or less than -100%.) When you set `AbsWeight` to `True`, this is the absolute value by which to boost the weight and it is then not limited by +/- 100.
`fieldName` | The name of the field that must be present (and must contain the proper value) for the document relevance to be boosted.

## Example

    FieldText=BIASVAL{Cambridge,10}:TOWN

A document whose `TOWN` field value is `Cambridge` has its weighting increased by 10% (although the weighting cannot go over 100%).

    FieldText=BIASVAL{Cambridge,10}:TOWN+BIASVAL{London,-10}:TOWN

A document whose `TOWN` field value is `Cambridge` has its weighting increased by 10%, and a document whose `TOWN` field value is `London` has its weighting decreased by 10%. This example shows that biases can be negative as well as positive, and that you can include more than one set of parameters with the specifier.

_FT_HTML5_bannerTitle.htm