R/quagpa.R

In lmomco: L-Moments, Censored L-Moments, Trimmed L-Moments, L-Comoments, and Many Distributions

"quagpa" <-
function(f,para,paracheck=TRUE) {
    if(! check.fs(f)) return()
    if(paracheck == TRUE) {
      if(! are.pargpa.valid(para)) return()
    }
    XI <- para$para[1]
    A  <- para$para[2]
    K  <- para$para[3]

    Y <- suppressWarnings( -log(1 - f) )

    ZERO <- sqrt(.Machine$double.eps) # following Tony Ladson, March 2016
    if(abs(K) > ZERO) Y <- ( 1 - exp(-K*Y) ) / K # following Tony Ladson, March 2016
    x <- XI + A*Y

    x[f == 0] <- XI
    x[f == 1 & K > 0] <- XI + A/K
    names(x) <- NULL
    return(x)
}