R: Computation of lower and upper approximations of decision...

BC.LU.approximation.RST {RoughSets} | R Documentation

## Computation of lower and upper approximations of decision classes

### Description

This function implements a fundamental part of RST: computation of lower and upper approximations. The lower and upper approximations determine whether the objects can be certainty or possibly classified to a particular decision class on the basis of available knowledge.

### Usage

    BC.LU.approximation.RST(decision.table, IND)

### Arguments

`decision.table` | an object inheriting from the `"DecisionTable"` class, which represents a decision system. See `SF.asDecisionTable`.
`IND` | an object inheriting from the `"IndiscernibilityRelation"` class, which represents indiscernibility clasees in the data.

### Details

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`.

### Value

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

- `lower.approximation`: a list with indices of data instances included in lower approximations of decision classes.

- `upper.approximation`: a list with indices of data instances included in upper approximations of decision classes.

- `type.model`: a character vector identifying the type of model which was used. In this case, it is `"RST"` which means the rough set theory.

### Author(s)

Andrzej Janusz

### References

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

### See Also

`BC.IND.relation.RST`, `BC.LU.approximation.FRST`

### Examples

    #######################################
    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 approximations:
    roughset <- BC.LU.approximation.RST(hiring.data, IND.A)
    roughset

[Package RoughSets version 1.3-7 Index]