sim.NormalIG.Hierarchical {iMRMC}R Documentation

Simulate an MRMC data set comparing two modalities by a hierarchical model

Description

This procedure simulates an MRMC data set for an MRMC agreement study comparing two modalities. It is a hierarchical model that consists of two interaction terms: reader-case interaction and modality-reader-case-replicate interaction. Both interaction terms are conditionally normally distributed, with the case(-related) factor contributing to the conditional mean and the reader(-related) factor contributing to the conditional variance. The case effect is normally distributed, while the reader effect is an inverse-gamma.

The Hierarchical Inverse-Gamma model is described in this paper:

Usage

sim.NormalIG.Hierarchical(
  config,
  R = NULL,
  AR = NULL,
  BR = NULL,
  is.within = FALSE
)

Arguments

config

[list] of simulation parameters:

  • Experiment labels and size

    • modalityID: [vector] label modality A and B.

    • nR: [num] number of readers

    • nC: [num] number of cases

    • C_dist: [chr] distribution of the case. Default C_dist="normal"

  • Mean and fixed effects:

    • mu: [num] grand mean

    • tau_A: [num] modality A

    • tau_B: [num] modality B

  • Reader-case interaction term

    • sigma_C: [num] std of case factor (if C_dist="normal")

    • a_C: [num] alpha for distribution of case (if C_dist="beta")

    • b_C: [num] beta for distribution of case (if C_dist="beta")

    • alpha_R: [num] shape parameter for reader

    • beta_R: [num] scale parameter for reader

  • Modality-reader-case-replicate interaction term for modality A

    • sigma_C.A: [num] std of case factor (if C_dist="normal")

    • a_C.A: [num] alpha for distribution of case (if C_dist="beta")

    • b_C.A: [num] beta for distribution of case (if C_dist="beta")

    • alpha_R.A: [num] shape parameter for reader

    • beta_R.A: [num] scale parameter for reader

  • Modality-reader-case-replicate interaction term for modality B

    • sigma_C.B: [num] std of case factor (if C_dist="normal")

    • a_C.B: [num] alpha for distribution of case (if C_dist="beta")

    • b_C.B: [num] beta for distribution of case (if C_dist="beta")

    • alpha_R.B: [num] shape parameter for reader

    • beta_R.B: [num] scale parameter for reader

  • Scales for the case related terms and interaction terms

    • C_scale: [num] weight for the case factor

    • RC_scale: [num] weight for the reader-case interaction term

    • tauC_scale: [num] weight for the modality-case term

    • tauRCE_scale: [num] weight for the modality-reader-case-replicate interaction term

R

[vector] of size nR of reader factors pre-generated from a gamma(alpha_R, beta_R) distribution to allow the reader factor to be fixed across multiple simulations. Default = NULL

AR

[vector] of size nR of modality-reader interaction terms pre-generated from a gamma(alpha_R.A, beta_R.A) distribution to allow the modality-reader interaction terms to be fixed across multiple simulations the modality-reader interaction. Default = NULL

BR

[vector] of size nR of modality-reader interaction terms pre-generated from a gamma(alpha_R.B, beta_R.B) distribution to allow the modality-reader interaction terms to be fixed across multiple simulations the modality-reader interaction. Default = NULL

is.within

[bol] whether the data are within-modality (A==B). In this case the modality-reader and modality-case interaction terms will be the same. Default = FALSE

Details

The model has the following structure: X.ijkl = mu + m.i + RC.jk + mRCE.ijkl

Value

df [data.frame] with nR x nC x 2 rows including


[Package iMRMC version 2.1.0 Index]