R/are.parln3.valid.R

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

"are.parln3.valid" <-
function(para,nowarn=FALSE) {
    if(! is.ln3(para)) return(FALSE)
    if(any(is.na(para$para))) return(FALSE)

    ZETA <- para$para[1]
    MU   <- para$para[2]
    SIG  <- para$para[3]

    ETA   <- exp(MU)
    # Now the conventional location, scale, shape
    XI <- ZETA + ETA # get the parameters
    ALPHA <- ETA*SIG # into the GNO domain, we can do
    K     <- -SIG # a check using the first two L-moments

    AK <- (ALPHA/K); EK <- exp(K^2/2)
    LAM1 <- XI + AK*(1-EK)
    LAM2 <-      AK*(  EK) * (1-2*pnorm(-K/sqrt(2)))

    op <- options()
    GO <- TRUE
    if(nowarn == TRUE) options(warn=-1)
    if(SIG <= 0) {
       warning("Parameter SIG is not > 0, invalid")
       GO <- FALSE
    }
    if(! is.finite(LAM1) | ! is.finite(LAM2)) {
       warning("Parameter LAM1 or LAM2 is not finite, invalid")
       GO <- FALSE
    } else {
       if(ZETA >= (LAM1 + LAM2)) {
          warning("Parameter ZETA is not < LAM1 + LAM2, invalid")
          GO <- FALSE
       }
    }
    options(op)
    if(GO) return(TRUE)
    return(FALSE)
}