Create a bootstrap sample, perform multivariate QTL scan, and calculate log10 LRT statistic
boot_pvl( probs, pheno, addcovar = NULL, kinship = NULL, start_snp = 1, n_snp, pleio_peak_index, nboot = 1, max_iter = 10000, max_prec = 1/1e+08, cores = 1 )
founder allele probabilities three-dimensional array for one chromosome only (not a list)
n by d matrix of phenotypes
n by c matrix of additive numeric covariates
a kinship matrix, not a list
positive integer indicating index within probs for start of scan
number of (consecutive) markers to use in scan
positive integer index indicating genotype matrix for bootstrap sampling. Typically acquired by using `find_pleio_peak_tib`.
number of bootstrap samples to acquire and scan
maximum number of iterations for EM algorithm
stepwise precision for EM algorithm. EM stops once incremental difference in log likelihood is less than max_prec
number of cores to use when calling mclapply to parallelize the bootstrap analysis.
numeric vector of (log) likelihood ratio test statistics from `nboot_per_job` bootstrap samples
Performs a parametric bootstrap method to calibrate test statistic values in the test of pleiotropy vs. separate QTL. It begins by inferring parameter values at the `pleio_peak_index` index value in the object `probs`. It then uses these inferred parameter values in sampling from a multivariate normal distribution. For each of the `nboot` sampled phenotype vectors, a two-dimensional QTL scan, starting at the marker indexed by `start_snp` within the object `probs` and extending for a total of `n_snp` consecutive markers. The two-dimensional scan is performed via the function `scan_pvl_clean`. For each two-dimensional scan, a log10 likelihood ratio test statistic is calculated. The outputted object is a vector of `nboot` log10 likelihood ratio test statistics from `nboot` distinct bootstrap samples.
Knott SA, Haley CS (2000) Multitrait least squares for quantitative trait loci detection. Genetics 156: 899–911.
Walling GA, Visscher PM, Haley CS (1998) A comparison of bootstrap methods to construct confidence intervals in QTL mapping. Genet. Res. 71: 171–180.
n <- 50 pheno <- matrix(rnorm(2 * n), ncol = 2) rownames(pheno) <- paste0("s", 1:n) colnames(pheno) <- paste0("tr", 1:2) probs <- array(dim = c(n, 2, 5)) probs[ , 1, ] <- rbinom(n * 5, size = 1, prob = 0.2) probs[ , 2, ] <- 1 - probs[ , 1, ] rownames(probs) <- paste0("s", 1:n) colnames(probs) <- LETTERS[1:2] dimnames(probs)[] <- paste0("m", 1:5) boot_pvl(probs = probs, pheno = pheno, start_snp = 1, n_snp = 5, pleio_peak_index = 3, nboot = 1, cores = 1)#>  1.826634