R/easyBoundaryFunc.R

In AppliedPredictiveModeling: Functions and Data Sets for 'Applied Predictive Modeling'

easyBoundaryFunc <- function(n,
                             intercept = 0,
                             interaction = 2) {
  sigma <- matrix(c(2, 1.3, 1.3, 2), 2, 2)
  
  tmpData <- data.frame(mvrnorm(n = n, c(0, 0), sigma))
  xSeq <- seq(-4, 4, length = 40)
  plotGrid <- expand.grid(x = xSeq, y = xSeq)
  zFoo <- function(x, y)
    intercept - 4 * x + 4 * y + interaction * x * y
  z2p <- function(x)
    1 / (1 + exp(-x))
  
  tmpData$prob <- z2p(zFoo(tmpData$X1, tmpData$X2))
  tmpData$class <-
    factor(ifelse(runif(length(tmpData$prob)) <= tmpData$prob, "Class1", "Class2"))
  tmpData
}