R/elaborator_perform_ttest.R

In elaborator: A 'shiny' Application for Exploring Laboratory Data

#' Performs t-test for changes of a laboratory parameter between two visits
#'
#' @description
#' This function is mostly useful for generating the quantitative trend analysis plots. It returns the output of a t-test result used for colorizing the background of the plots.
#'
#'@param data data set
#'@param treatment name of treatment group
#'@param lab_parameter name of laboratory parameter
#'@param Visit1 name of visit time point one
#'@param Visit2 name of visit time point two
#'@param lab_column column name of data which includes the laboratory parameter names
#'
#'@return A list of class "htest" with the results of the t-test.
#'
#'@keywords internal

elaborator_perform_ttest <- function(data, treatment, lab_parameter, Visit1 = "Randomization", Visit2 = "End of Treatment", lab_column){

  datasub <- data[data$TRTP == treatment & data[,lab_column] == lab_parameter,]

  differ <- unlist(sapply(unique(datasub$SUBJIDN), function(z){
    res <- datasub$LBORRES[datasub$SUBJIDN == z & datasub$AVISIT == Visit1] -
      datasub$LBORRES[datasub$SUBJIDN == z & datasub$AVISIT == Visit2]
    if (length(res) == 0 || is.na(res)) return(NA) else return(res)
  }))
  testres <- stats::t.test(x = differ)
}