R/center.R

In dr-JT/datawrangling: Common functions for transforming, merging, binding, evaluating, and re-organizing dataframes

#' Create a column of centered variables
#'
#' This function centers a variable around the mean. To create z-scores,
#' specify `standardize=TRUE`
#' A new column will be created with the centered values.
#' There is also the option to center within context.
#' @param x dataframe
#' @param variables c() of columns to standardize
#' @param standardize Logical. Do you want to calculate
#' zscores? (Default = FALSE)
#' @param drop Drop original non-centered variables
#' @param suffix Suffix to add at the end of the column names. Default = NULL
#' @export
#'

center <- function(x, variables = c(colnames(x)), standardize = FALSE,
                   drop = FALSE, suffix = NULL){
  # Perform this function for each variable specified
  for (variable in colnames(x[variables])){
    # Calculate centered scores using the scale() function
    x <- dplyr::mutate(x,
                       hold = scale(get(variable), center = TRUE,
                                    scale = standardize))
    x$hold <- as.vector(x$hold)
    if (drop == TRUE) {
      x <- x[, -which(colnames(x) == variable)]
    }
    if (standardize == FALSE){
      if (is.null(suffix)) {
        names(x)[which(names(x) == "hold")] <- paste(variable, "_c", sep = "")
      } else {
        names(x)[which(names(x) == "hold")] <- paste(variable, suffix, sep = "")
      }

    } else if (standardize == TRUE){
      if (is.null(suffix)) {
        names(x)[which(names(x) == "hold")] <- paste(variable, "_z", sep = "")
      } else {
        names(x)[which(names(x) == "hold")] <- paste(variable, suffix, sep = "")
      }

    }
  }

  return(x)
}