  The relation between wildfire orientation and size is analyzed by means of a
nonparametric test for directional-linear independence. The test statistic is
designed for assessing the independence between two random variables of
different nature, specifically directional (fire orientation, circular or
spherical, as particular cases) and linear (fire size measured as burnt area,
scalar), based on a directional-linear nonparametric kernel density estimator.
In order to apply the proposed methodology in practice, a resampling procedure
based on permutations and bootstrap is provided. The finite sample performance
of the test is assessed by a simulation study, comparing its behavior with
other classical tests for the circular-linear case. Finally, the test is
applied to analyze wildfire data from Portugal.
