RregressPkg: Functions to Assist in Linear Regression

#' @title bloodpress data
#'
#' @description
#' The data set of predictors originates
#' from [PennState Eberly College of Science](https://online.stat.psu.edu/stat501/lesson/welcome-stat-501)
#' Lesson 12: Multicollinearity & Other Regression Pitfalls.
#'
#' The dataframe consists of 20 individuals with high blood pressure. Here
#' are the column measurements:
#'
#'\tabular{ll}{
#'  \strong{Pt} \tab observation index \cr
#'  \strong{BP} \tab blood pressure , in mm Hg \cr
#'  \strong{Age} \tab age in years \cr
#'  \strong{Weight} \tab weight in kg \cr
#'  \strong{BSA} \tab body surface area in sq m \cr
#'  \strong{Dur} \tab duration of hypertension in years \cr
#'  \strong{Pulse} \tab basal pulse in beats per minute \cr
#'  \strong{Stress} \tab stress
#'}
"bloodpress"
#'
#' @title Therms18 data
#'
#' @description
#' The dataframe consists of 2500 observations with 2 columns
#'  on ratings for President Obama and President Trump. The ratings'
#'  scale range from 0 to 100 for unfavorable to favorable.
#'
#' \tabular{ll}{
#'  \strong{ftobama} \tab measures for President Obama \cr
#'  \strong{fttrump} \tab measures for President Trump
#' }
"Therms18"
#'
#' @title advertising data
#'
#' @description
#' The dataframe consists of 200 observations with 5 columns on
#' advertising expenditures and sales (in 100s dollars) from 3
#' different media: TV, radio, and newspaper.
#'
#'\tabular{ll}{
#'  \strong{V1} \tab numeric observation index\cr
#'  \strong{TV} \tab numeric expenditure for TV\cr
#'  \strong{radio} \tab numeric expenditure for radio\cr
#'  \strong{newspaper} \tab numeric expenditure for newspaper\cr
#'  \strong{sales} \tab numeric resulting sales
#'}
"advertising"
#'
#' @title pilots data
#'
#' @description
#' The dataframe consists of 40 observations with 7 columns.
#' Twenty engineer apprentices and twenty pilots were given six tests.
#' The tests measured the following attributes:
#'
#' \enumerate{
#'   \item Intelligence
#'   \item Form Relations
#'   \item Dynamometer
#'   \item Dotting
#'   \item Sensory Motor Coordination
#'   \item Perservation
#' }
#'
#' The data were obtained from the companion FTP site of the book Methods of
#' Multivariate Analysis by Alvin Renche.
#'
#' The dataframe contains these 6 test scores plus a 7th column indicating
#' if the observation is an "Apprentice" or "Pilot".
#'
"pilots"