# BC.positive.reg.RST: Computation of a positive region In janusza/RoughSets: Data Analysis Using Rough Set and Fuzzy Rough Set Theories

## Description

This function implements a fundamental part of RST: computation of a positive region and the degree of dependency. This function can be used as a basic building block for development of other RST-based methods. A more detailed explanation of this notion can be found in `A.Introduction-RoughSets`.

## Usage

 `1` ```BC.positive.reg.RST(decision.table, roughset) ```

## Arguments

 `decision.table` an object inheriting from the `"DecisionTable"` class, which represents a decision system. See `SF.asDecisionTable`. `roughset` an object inheriting from the `"LowerUpperApproximation"` class, which represents lower and upper approximations of decision classes in the data. Such objects are typically produced by calling the `BC.LU.approximation.RST` function.

## Value

An object of a class `"PositiveRegion"` which is a list with the following components:

• `positive.reg`: an integer vector containing indices of data instances belonging to the positive region,

• `degree.dependency`: a numeric value giving the degree of dependency,

• `type.model`: a varacter vector identifying the utilized model. In this case, it is `"RST"` which means the rough set theory.

Andrzej Janusz

## References

Z. Pawlak, "Rough Sets", International Journal of Computer and Information Sciences, vol. 11, no. 5, p. 341 - 356 (1982).

`BC.IND.relation.RST`, `BC.LU.approximation.RST`, `BC.LU.approximation.FRST`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16``` ```######################################################## data(RoughSetData) hiring.data <- RoughSetData\$hiring.dt ## We select a single attribute for computation of indiscernibility classes: A <- c(2) ## compute the indiscernibility classes: IND.A <- BC.IND.relation.RST(hiring.data, feature.set = A) ## compute the lower and upper approximation: roughset <- BC.LU.approximation.RST(hiring.data, IND.A) ## get the positive region: pos.region = BC.positive.reg.RST(hiring.data, roughset) pos.region ```