RoughSets (version 1.0-0)

D.discretization.RST: The wrapper function of discretization methods

Description

It is a wrapper function collecting all discretization methods based on RST. It provides an additional interface that allows users to use the methods of the discretization easily.

Usage

D.discretization.RST(decision.table,
    type.method = "unsupervised.quantiles", ...)

Arguments

decision.table

a "DecisionTable" class representing a decision table. See SF.asDecisionTable.

type.method

one of the following methods:

• "global.discernibility": SeeD.global.discernibility.heuristic.RST.
• "local.disc.matrix": See

...

other parameters related to the corresponding methods.

Value

• A class "Discretization". See D.local.discernibility.matrix.RST.

Details

Discretization is used to convert continuous attributes into nominal ones in an information system. It is very important to perform this process since any methods based on rough set theory need nominal attributes to compute the indiscernibility relation or perform other functions. Furthermore, in order to avoid loss of information, in rough set theory point of view, the discernibility relation among objects is maintained.

It should be noted that the output of this function is a class containing cut values. In order to generate a new decision table, the function SF.applyDecTable is executed.

See Also

BC.LU.approximation.RST, BC.LU.approximation.FRST

Examples

#################################################################
## Example: Determine cut values and generate new decision table
#################################################################
dt.ex1 <- data.frame(c(1, 2, 3, 3, 4, 5, 6, 7, 7, 8), c(2,5, 7, 6, 6, 6, 1, 8, 1, 1),
                             c(3, 5, 1, 1, 3, 6, 8, 8, 1, 1), c(0, 1, 2, 1, 0, 1, 2, 2, 0, 0))
colnames(dt.ex1) <- c("a1", "a2", "a3", "d")
decision.table <- SF.asDecisionTable(dataset = dt.ex1, decision.attr = 4, indx.nominal = c(4))

cut.values <- D.discretization.RST(decision.table, type.method = "global.discernibility")

## generate new decision table
new.decTable <- SF.applyDecTable(decision.table, cut.values)