The types of designs supported here are latin hypercube designs of different types. The simple designs produced by [grid_latin_hypercube()] are space-filling but don't guarantee or optimize any other properties. [grid_space_filling()] might be able to produce designs that discourage grid points from being close to one another. There are a lot of methods for doing this, such as maximizing the minimum distance between points (see Husslage et al 2001). [grid_max_entropy()] attempts to maximize the determinant of the spatial correlation matrix between coordinates.
Latin hypercube and maximum entropy designs use random numbers to make the designs.
By default, [grid_space_filling()] will try to use a pre-optimized space-filling design from https://www.spacefillingdesigns.nl/
(see Husslage et al, 2011) or using a uniform design. If no pre-made design is available, then a maximum entropy design is created.
library(tidymodels)
Also note that there may a difference in grids depending on how the function is called. If the call uses the parameter objects directly the possible ranges come from the objects in dials
. For example:
mixture() set.seed(283) mix_grid_1 <- grid_latin_hypercube(mixture(), size = 1000) range(mix_grid_1$mixture)
However, in some cases, the parsnip
and recipe
packages overrides the default ranges for specific models and preprocessing steps. If the grid function uses a parameters
object created from a model or recipe, the ranges may have different defaults (specific to those models). Using the example above, the mixture
argument above is different for glmnet
models:
library(parsnip) library(tune) # When used with glmnet, the range is [0.05, 1.00] glmn_mod <- linear_reg(mixture = tune()) %>% set_engine("glmnet") set.seed(283) mix_grid_2 <- glmn_mod %>% extract_parameter_set_dials() %>% grid_latin_hypercube(size = 1000) range(mix_grid_2$mixture)
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