| simdata87 {miWQS} | R Documentation |
Simulated Dataset 87
Description
The 87th dataset from the simulation study with 10 percent of observations were below the detection limit (BDL) based of a real epidemiological dataset. Out of 1000 subjects, fourteen correlated chemicals are completely observed (in X.true). In this simulation design, each chemical was simulated from independent normal distributions.
BDLs were created using the bottom 10th percentile of the true data. Three covariates are considered: the child’s age, the child’s sex (Male/Female), and the child’s ethnicity/race (White, Non-Hispanic White, and Other). After creating a model matrix, male white newborns (age = 0) serves as the reference. The age is simulated from a normal with mean of 3.78 and standard deviation of 1.85 truncated between 0 and 8. The categorical variables are simulated from independent binomial distributions. The outcome will be simulated using a logistic WQS model with complete data:
logit(\mu_{i}) = -1.25 + log(1.75)*WQS_{i} + 0.032*z_{age}+ -0.0285*z_{sex} + 0.540*z_{His} + 0.120*z_{other}
where
WQS_{i}= \Sigma_{j=1}^{c}(w_{j}*q_{ij})
with four of the 14 weights w_j's being 0.25 and the rest 0. The q_ij refers to the quantile score of the jth chemical in the ith subject.
Usage
data(simdata87)
Format
A list that contains:
y.scenario: A binary outcome (1 = case, 0 = control)
X.true: 14 chemicals; complete data.
X.bdl: 14 chemicals with NA's subbed for the bottom 10th percentile of the true values.
DL: The detection limit. Here, found to be the 10th percentile of X.true
n0: A vector of length 14 indicating the number of non-detects.
delta: A vector of length 14 indicating whether the chemical is observed (1) or not (0)
Z.sim: A data-frame of covariates consisting of:
Age: A continuous covariate of child's age , simulated using normal with mean of 3.78 and sd of 1.85, truncated between 0 and 8, the maximum age of the case.
Female: Binary variable child's sex, simulated using the proportion of females (0.42) by binomial distribution.
Hispanic, Non-Hispanic_Others: Two indicator variables of child's race/ethnicity, sampled from independent binomial distributions (proportion of Hispanic: 0.33; proportion of Other: 0.23).
time: The time required to simulate the data.
References
Ward, M. H., Colt, J. S., Metayer, C., Gunier, R. B., Lubin, J., Crouse, V., … Buffler, P. A. (2009). Residential Exposure to Polychlorinated Biphenyls and Organochlorine Pesticides and Risk of Childhood Leukemia. Environmental Health Perspectives, 117(6), 1007–1013. https://doi.org/10.1289/ehp.0900583
Examples
simdata87 <- data(simdata87)