mathStatica extends naturally to a multivariate setting. To illustrate, let us suppose that and have joint pdf with support , :
where parameter α is such that . This is known as a Gumbel bivariate Exponential distribution. Here is a plot of :
Fig. 1: A Gumbel bivariate Exponential pdf when
Here is the cdf, namely :
Here is , the covariance between and :
More generally, here is the variance-covariance matrix:
Here is the marginal pdf of :
Here is the conditional pdf of , given :
Here is the bivariate mgf :
Differentiating the mgf is one way to derive moments. Here is the product moment :
which we could otherwise have found directly with:
Multivariate transformations pose no problem to mathStatica either. For instance, let and denote transformations of and . Then our transformation equation is:
Using Transform, we can find the joint pdf of random variables and , denoted :
while the extremum of the domain of support of the new random variables are: