rPref (version 0.4)

pred_succ: Predecessor and successor functions

Description

Function for traversing the BTG (Better-Than-Graph) of a preference.

Usage

init_pred_succ(df, p)
hasse_pred(p, v)
hasse_succ(p, v)
all_pred(p, v)
all_succ(p, v)

Arguments

df

A dataframe characterizing the basic set wherein predecessors/sucessors are seached.

p

A preference. Worse tuples in the induced order are succesors and better tuples are predecessors.

v

A numeric vector of indices in df. This describes the set of tuples for which predecessors/successors are searched.

Details

These functions return the predecessors and successors in the Better-Than-Graph of a preference which can be plotted via get_btg. Before any of the successor/predecessor functions can be used the initialization has to be called as follows:

init_pred_succ(p, df)

There p is a preference object and df a dataframe. This statement calculates the Better-Than-Relation on df w.r.t. p. Afterwards the subsequent predecessor and sucessor functions can be called. The return values and the values of v are subsets of 1:nrow(df) and characerise a subset of tuples in df.

[object Object],[object Object],[object Object],[object Object]

Examples

# Preference on mtcars for high mpg and low weight
p <- high(mpg) * low(wt)
init_pred_succ(mtcars, p)

# Helper to show mpg/hp values
show_vals <- function(x) mtcars[x,c('mpg','wt')]

# Pick some tuple "in the middle"
show_vals(10)

# Show (direct) predecessors/successors
show_vals(hasse_pred(p, 10)) # Next better car
show_vals(hasse_succ(p, 10)) # Next worse car
show_vals(all_pred(p, 10))   # All better cars
show_vals(all_succ(p, 10))   # All worse cars