R/screeplot.R

In psy: Various Procedures Used in Psychometrics

#' @export
scree.plot <-
  function(namefile, title="Scree Plot", type="R", use="complete.obs", simu="F")
  {

    mat <- namefile
    if (use=="complete.obs") mat <- na.omit(namefile)

    if (type=="R") eigenval <- eigen(cor(mat,use="pairwise.complete.obs"), symmetric=TRUE)$values
    if (type=="V") eigenval <- eigen(cov(mat,use="pairwise.complete.obs"), symmetric=TRUE)$values
    if (type=="E") eigenval <- namefile
    if (type=="M") eigenval <- eigen(namefile, symmetric=TRUE)$values

    nev <- length(eigenval)
    plot(eigenval, type = "b", pch = 16, bty = "o", main = title, xlab = "Dimension", ylab = "Eigenvalue")
    lines(c(1,nev),c(1,1),lty=2)

    if (is.numeric(simu) && (type=="R"))
    {
      n <- dim(mat)[1]
      p <- dim(mat)[2]

      matsimu <- matrix(nrow=n,ncol=p)
      int <- rep(1,n*p)
      attr(int,"dim") <- c(n,p)
      mat <- pmax(as.matrix(mat),int)

      for(i in 1:simu)
      {
        matnorm <- rnorm(n*p)
        attr(matnorm,"dim") <- c(n,p)
        matsimu <- (mat/mat)*matnorm
        eigenval <- eigen(cor(matsimu,use="pairwise.complete.obs"))$values
        points(eigenval,type="l")
      }
    }
  }