ctab: 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"

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.

Value

All ctab functions return an object of class ctab.

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.

Examples

Run this code

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,"/")