R: non-regularized estimation methods for the Ising Model

EstimateIsing {IsingSampler}

R Documentation

non-regularized estimation methods for the Ising Model

Description

This function can be used for several non-regularized estimation methods of the Ising Model. See details.

Usage

EstimateIsing(data, responses, beta = 1, method = c("pl", "uni",
                 "bi", "ll"), adj = matrix(1, ncol(data), ncol(data)),
                 ...)
EstimateIsingUni(data, responses, beta = 1, adj = matrix(1, ncol(data),
                 ncol(data)), ...)
EstimateIsingBi(data, responses, beta = 1, ...)
EstimateIsingPL(data, responses, beta = 1, ...)
EstimateIsingLL(data, responses, beta = 1, adj = matrix(1, ncol(data),
                 ncol(data)), ...)

Arguments

`data`	Data frame with binary responses to estimate the Ising model over
`responses`	Vector of length two indicating the response coding (usually `c(0L, 1L)` pr `c(-1L, 1L)`)
`beta`	Inverse temperature parameter
`method`	The method to be used. `pl` uses pseudolikelihood estimation, `uni` sequential univariate regressions, `bi` bivariate regressions and `ll` estimates the Ising model as a loglinear model.
`adj`	Adjacency matrix of the Ising model.
`...`	Arguments sent to estimator functions

Details

The following algorithms can be used (see Epskamp, Maris, Waldorp, Borsboom; in press).

pl: Estimates the Ising model by maximizing the pseudolikelihood (Besag, 1975).
uni: Estimates the Ising model by computing univariate logistic regressions of each node on all other nodes. This leads to a single estimate for each threshold and two estimates for each network parameter. The two estimates are averaged to produce the final network. Uses glm.
bi: Estimates the Ising model using multinomial logistic regression of each pair of nodes on all other nodes. This leads to a single estimate of each network parameter and $p$ estimates of each threshold parameter. Uses multinom.
ll: Estimates the Ising model by phrasing it as a loglinear model with at most pairwise interactions. Uses loglin.

Value

A list containing the estimation results:

`graph`	The estimated network
`thresholds`	The estimated thresholds
`results`	The results object used in the analysis

Author(s)

Sacha Epskamp (mail@sachaepskamp.com)

References

Epskamp, S., Maris, G., Waldorp, L. J., and Borsboom, D. (in press). Network Psychometrics. To appear in: Irwing, P., Hughes, D., and Booth, T. (Eds.), Handbook of Psychometrics. New York: Wiley.

Besag, J. (1975), Statistical analysis of non-lattice data. The statistician, 24, 179-195.

Examples

# Input:
N <- 5 # Number of nodes
nSample <- 500 # Number of samples

# Ising parameters:
Graph <- matrix(sample(0:1,N^2,TRUE,prob = c(0.7, 0.3)),N,N) * rnorm(N^2)
Graph <- Graph + t(Graph)
diag(Graph) <- 0
Thresholds <- rep(0,N)
Beta <- 1

# Response options (0,1 or -1,1):
Resp <- c(0L,1L)
Data <- IsingSampler(nSample,Graph, Thresholds)

# Pseudolikelihood:
resPL <- EstimateIsing(Data, method = "pl")
cor(Graph[upper.tri(Graph)], resPL$graph[upper.tri(resPL$graph)])

# Univariate logistic regressions:
resUni <- EstimateIsing(Data, method = "uni")
cor(Graph[upper.tri(Graph)], resUni$graph[upper.tri(resUni$graph)])

# bivariate logistic regressions:
resBi <- EstimateIsing(Data, method = "bi")
cor(Graph[upper.tri(Graph)], resBi$graph[upper.tri(resBi$graph)])

# Loglinear model:
resLL <- EstimateIsing(Data, method = "ll")
cor(Graph[upper.tri(Graph)], resLL$graph[upper.tri(resLL$graph)])

[Package IsingSampler version 0.2.1 Index]