GEVD-with-p1: Quantile function
qgev_p12(p, t1, t2, ymn, slope, sigma1, sigma2, xi)
Vector
a vector of probabilities at which to generate predictive quantiles
a vector of predictors for the mean
a vector of predictors for the sd
the location parameter of the function of the predictor
the slope of the function of the predictor
first coefficient for the sigma parameter of the distribution
second coefficient for the sigma parameter of the distribution
the shape parameter of the distribution