Third derivative of the log density Created by Stephen Jewson using Deriv() by Andrew Clausen and Serguei Sokol
gev_p123_logfddd(x, t1, t2, t3, v1, v2, v3, v4, v5, v6)
3d array
a vector of training data values
a vector of predictors for the mean
a vector of predictors for the sd
a vector of predictors for the shape
first parameter
second parameter
third parameter
fourth parameter
fifth parameter
sixth parameter