Compute the quantile function of Inverse gamma distribution
qinvGamma(p, a, b, lower.tail = TRUE, log.p = FALSE)
vector of probabilities
the shape parameter of the inverse gamma distribution
the scale parameter of the inverse gamm distribution
logical; if TRUE (default), probabilities are P[X > x], otherwise, P[X <= x].
FLASE (default) if TRUE, probabilities/densities p are returned as log(p)