conting (version 1.7)

index2model: Convert Between Index and Model Indicator

Description

These functions convert the binary vector, indicating which terms are in the current model, to the hexadecimal model indicator, and vice versa.

Usage

index2model(index)
model2index(model,dig)

Arguments

index

A binary vector, of the same length as the number of log-linear parameters in the maximal model, indicating which parameters are present in the model to be converted to a hexadecimal.

dig

A scalar argument giving the number of columns of the design matrix for the maximal model.

model

A character string giving a hexadecimal model indicator.

Value

index2model will return a hexadecimal model indicator.

model2index will return a binary vector, of the same length as the number of log-linear parameters in the maximal model, indicating which parameters are present in the model converted from hexadecimal.

Examples

# NOT RUN {
data(ScotPWID)
## Load the ScotPWID data

maximal.mod<-glm(y~(S1+S2+S3+S4+Region+Gender+Age)^2,family=poisson,contrasts=list(
S1="contr.sum",S2="contr.sum",S3="contr.sum",S4="contr.sum",
Region="contr.sum",Gender="contr.sum",Age="contr.sum"),data=ScotPWID,x=TRUE)
## Fit the maximal model containing all two-way interactions.

big.X<-maximal.mod$x
## Set the design matrix under the maximal model

index<-formula2index(big.X=big.X,
formula=~S1+S2+S3+S4+Region+Gender+Age+S1:S2+S1:Age+S2:Gender+S3:S4+S4:Age,
data=ScotPWID)
## Find the index under the model with the following interactions:
## S1:S2
## S1:Age
## S2:Gender
## S3:S4
## S4:Age

index
## Print the index, will get:
# [1] 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0

modind<-index2model(index)
## Find the hexadecimal model indicator
modind
## Print it, will get:
#[1] "1ff08a08"

## Convert back to index
model2index(model=modind,dig=length(index))
## Will get:
# [1] 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 1 0 0 0

# }