Set 3 double parameters in p_db using paradox package

Question

How can I set parameter with say 3 float values. For example I want to search parameter X for 0.99, 0.98 and 0.97.

For p_dbl there are lower and upper parameters but not values I can use.

For example something like (this doesn't work ofc):

p_dbl(c(0.99, 0.98, 0.97))

Answer 1

I am assuming you want to do this for tuning purposes. If you don't, you have to use a p_dbl() and set the levels as characters ("0.99", ...).

Note that the second solution that I am giving here is simply a shortcut for the first approach, where the transformation is explicitly defined. This means that the paradox package will create the transformation for you, similarly to how it is done in the first of the two solutions.

library(paradox)
library(data.table)

search_space = ps(
  a = p_fct(levels = c("0.99", "0.98", "0.97"), trafo = function(x, param_set) {
    switch(x,
      "0.99" = 0.99,
      "0.98" = 0.98,
      "0.97" = 0.97
    )
  })
)

design = rbindlist(generate_design_grid(search_space, 3)$transpose(), fill = TRUE)
design
#>       a
#> 1: 0.99
#> 2: 0.98
#> 3: 0.97
class(design[[1]])
#> [1] "numeric"
# the same can be achieves as follows:

search_space = ps(
  a = p_fct(levels = c(0.99, 0.98, 0.97))
)

design = rbindlist(generate_design_grid(search_space, 3)$transpose(), fill = TRUE)
design
#>       a
#> 1: 0.99
#> 2: 0.98
#> 3: 0.97
class(design[[1]])
#> [1] "numeric"

^{Created on 2023-02-15 with reprex v2.0.2}