R/uwSimpleReg.R

In jbirstler/biostatrpts: Functions for UW-Biostatistics Report Creation

#' Scatter Plot with Simple Linear Regression Line
#'
#' This function creates a scatter plot of two continuous variables and adds
#' the fitted simple linear regression line.
#'
#'
#' @param Data Data frame with response and dependent variable
#' @param respVar String of the response variable's name in Data
#' @param depVar String of the dependent variable's name in Data
#' @param printPVal Logical: TRUE indicates p-value for beta1 = 0 is printed in
#' margin of plot
#' @param printModel Logical: TRUE indicates fitted model is printed in margin
#' of plot
#' @param printRsq Logical: TRUE indicates multiple R-squared is printed in
#' margin of plot
#' @param returnList Logical: TRUE returns list of Coefficient and P-Value
#' @param ... Any other arguments that can be used by plot()
#' @return Plots a scatterplot and regression line.  Returns list of beta1
#' coefficient and p-value
#' @author University of Wisconsin-Madison Biostatistics and Medical
#' Informatics Department, Scott Hetzel M.S.
#' @seealso plot(), abline(), lm()
#' @export
#' @examples
#'
#'
#' Xvar <- rnorm(50, -10, 1)
#' Yvar <- 0.5 * Xvar + rnorm(50, 0, 1)
#'
#' dfLin <- data.frame(Xvar, Yvar)
#'
#' layout(1)
#' uwSimpleReg(
#'   Data = dfLin, respVar = "Yvar", depVar = "Xvar",
#'   main = "Example of uwSimpleReg",
#'   ylab = "Example Response", xlab = "Example Explanatory",
#'   ylim = NULL, xlim = NULL, printPVal = TRUE, printModel = TRUE, printRsq = TRUE
#' )
uwSimpleReg <- function(Data, respVar, depVar, printPVal = TRUE, printModel = TRUE, printRsq = TRUE, returnList = TRUE,
                        ...) {
  lm1 <- lm(Data[[respVar]] ~ Data[[depVar]], data = Data)

  plot(x = Data[[depVar]], y = Data[[respVar]], tcl = NA, ...)

  box()
  abline(lm1)

  if (printPVal) {
    pval <- round(summary(lm1)$coef[2, 4], 3)
    if (pval == 0) {
      mtext("p < 0.001", side = 3, line = 0, cex = 0.7)
    } else {
      mtext(paste("p = ", pval, sep = ""), side = 3, line = 0, cex = 0.7)
    }
  }
  if (printModel) {
    model <- paste("Fitted Regression Line: Y = ", round(summary(lm1)$coef[2, 1], 3), "*X ", if (summary(lm1)$coef[
      1,
      1
    ] < 0) {
      round(summary(lm1)$coef[1, 1], 3)
    } else {
      paste("+ ", round(summary(lm1)$coef[1, 1], 3), sep = "")
    }, sep = "")
    mtext(model, side = 3, line = 0.8, cex = 0.7)
  }
  if (printRsq) {
    mtext(paste("R squared = ", round(summary(lm1)$r.squared, 3), sep = ""), side = 1, cex = 0.7)
  }
  if (returnList) {
    return(list(Coef = round(summary(lm1)$coef[2, 1], 4), PVal = summary(lm1)$coef[2, 4]))
  }
}