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Simulate data from beta interval models

Source: R/simulate.R
brs_sim.Rd

Simulates interval-censored responses from fixed- or variable-dispersion beta regression models.

Usage

brs_sim(
  formula,
  data,
  beta,
  phi = 1/5,
  zeta = NULL,
  link = "logit",
  link_phi = "logit",
  ncuts = 100L,
  lim = 0.5,
  repar = 2L,
  delta = NULL
)

Arguments

formula

Model formula with one (mean) or two parts (mean | precision). A left-hand-side response is allowed but ignored.

data

Data frame with predictor variables.

beta

Numeric vector of mean-model coefficients.

phi

Scalar dispersion parameter (link scale), used only for one-part formulas.

zeta

Numeric vector of precision-model coefficients (link scale), required for two-part formulas.

Mean link function.

Precision link function.

ncuts

Number of scale categories.

lim

Half-width used in interval construction.

repar

Reparameterization scheme.

delta

Forced censoring type (0,1,2,3) or NULL.

Value

A data frame with columns left, right, yt, y, delta, plus simulated predictor columns from the model matrices. When delta != NULL, the output carries attr(, "is_prepared") = TRUE.

Details

The model structure is controlled by formula in the same style as brs:

  • one-part formula (~ x1 + x2 or y ~ x1 + x2): fixed dispersion using scalar phi.

  • two-part formula (~ x1 + x2 | z1 or y ~ x1 + x2 | z1): variable dispersion using coefficient vector zeta.

The delta argument can force a single censoring type (0,1,2,3) for all observations; otherwise, censoring is classified automatically from simulated scale values via brs_check.

References

Hawker, G. A., Mian, S., Kendzerska, T., and French, M. (2011). Measures of adult pain: Visual Analog Scale for Pain (VAS Pain), Numeric Rating Scale for Pain (NRS Pain), McGill Pain Questionnaire (MPQ), Short-Form McGill Pain Questionnaire (SF-MPQ), Chronic Pain Grade Scale (CPGS), Short Form-36 Bodily Pain Scale (SF-36 BPS), and Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP). Arthritis Care and Research, 63(S11), S240-S252. doi:10.1002/acr.20543.

Hjermstad, M. J., Fayers, P. M., Haugen, D. F., et al. (2011). Studies comparing Numerical Rating Scales, Verbal Rating Scales, and Visual Analogue Scales for assessment of pain intensity in adults: a systematic literature review. Journal of Pain and Symptom Management, 41(6), 1073-1093. doi:10.1016/j.jpainsymman.2010.08.016.

Examples

set.seed(42)
n <- 200
dat <- data.frame(x1 = rnorm(n), x2 = rnorm(n), z1 = runif(n))

# Fixed dispersion
sim_fixed <- brs_sim(
  formula = ~ x1 + x2, data = dat,
  beta = c(0.2, -0.5, 0.3), phi = 1 / 5
)

# Variable dispersion
sim_var <- brs_sim(
  formula = ~ x1 + x2 | z1, data = dat,
  beta = c(0.2, -0.5, 0.3), zeta = c(0.5, -0.5)
)