R/chisq_wrap.R

In prestevez/estevez: Victimisation Analysis and Reporting

#' Chi-square wrapper
#'
#' This function is wraps the \code{\link{chisq.test}} function
#' from the \code{stats} package to automatically simulate the
#' p-value if the data provided does not comply with the assumptions
#' of the Chi-square test, specifically that there is at least
#' one cell with less than 5 expected counts.
#' @param x a numeric vector or matrix. x and y can also both be factors.
#' @param y a numeric vector; ignored if x is a matrix. If x is a factor,
#'     y should be a factor of the same length.
#' @param ... passes options to the function
#' @keywords chi-square
#' @export
#' @examples
#' chisq_wrap(testdata$extortion_victim, testdata$size)
#'
#' # x is a matrix or an object that can be coerced into a matrix
#' t <- table(testdata$extortion_victim, testdata$size)
#' chisq_wrap(t)
#'
#' # Pass number of replicates to be used if simulation is required
#' chisq_wrap(t, B = 1000)

chisq_wrap <- function(x, y = NULL, ...)
{
    tc <- tryCatch(chisq.test(x, y, ...), warning = function(x) x)

    simul <- FALSE

    if(is(tc, "warning"))
    {
        simul <- TRUE
    }

    test <- chisq.test(x, y, simulate.p.value = simul, ...)

    return(test)
}