ctab {gRain}R Documentation

Representation of and operations on multidimensional tables

Description

General representation of multidimensional tables (by ctab objects). Operations on these include multiplication, division and marginalization.

Usage

ctab(varNames, nLevels, values = 1, normalize = c("none", "first", "all"), smooth = 0)
ctabop(t1, t2, op="*")
ctabmarg(t1, marg, normalize=FALSE)

## S3 method for class 'ptab':
varNames(x)
## S3 method for class 'ptab':
nLevels(x)
## S3 method for class 'ptab':
valueLabels(x)

Arguments

varNames Names of variables defining table
nLevels Levels of variables
values Table values
t1,t2,x Objects of class "ptab"
op Operation to perform. Either "*" or "/" (where 0/0=0)
marg Set of nodes to marginalize onto
normalize Should result be normalized, see 'Details' below.
smooth Should values be smoothed, see 'Details' below.

Details

A ctab object represents a table defined by a set of variables and their levels, together with the values of the table. E.g. f(a,b,c) can be a table with a,b,c representing levels of binary variable

If normalize="first" then for each configuration of the parents, "pa", the probabilities are normalized to sum to one. Thus f(a,b,c) becomes a conditional probability table of the form p(a|b,c). If normalize="all" then the sum over all entries of f(a,b,c) is one.

If smooth is non–zero then zero entries of values are replaced with smooth before normalization takes place.

Value

All ctab functions return an object of class ctab.

Author(s)

Søren Højsgaard, sorenh@agrsci.dk

See Also

cpt

Examples

t1 <- ctab(c("gender","answer"),list(c('male','female'),c('yes','no')), values=1:4)
t2 <- ctab(c("answer","category"), list(c('yes','no'),c(1,2)), values=1:4+10)
t3 <- ctab(c("category","foo"), c(2,2), values=1:4+100)

varNames(t1)
nLevels(t1)
valueLabels(t1)

ctabop(t1,t2, "*")
ctabop(t1,t2, "/")

tgender <- ctabmarg(t1, "gender")
t1
tgender
ctabop(t1,tgender,"/")

[Package gRain version 0.3.4 Index]