# README.md In paradox: Define and Work with Parameter Spaces for Complex Algorithms

Package website: release \| dev

Universal Parameter Space Description and Tools.

## Installation

``````remotes::install_github("mlr-org/paradox")
``````

## Usage

Create a simple ParamSet using all supported Parameter Types:

• integer numbers (`"int"`)
• real-valued numbers (`"dbl"`)
• truth values `TRUE` or `FALSE` (`"lgl"`)
• categorical values from a set of possible strings (`"fct"`)
• further types are only possible by using transformations.
``````ps = ParamSet\$new(
params = list(
ParamInt\$new(id = "z", lower = 1, upper = 3),
ParamDbl\$new(id = "x", lower = -10, upper = 10),
ParamLgl\$new(id = "flag"),
ParamFct\$new(id = "methods", levels = c("a","b","c"))
)
)
``````

Draw random samples / create random design:

``````generate_design_random(ps, 3)
#> <Design> with 3 rows:
#>    z         x  flag methods
#> 1: 1  7.660348 FALSE       b
#> 2: 3  8.809346 FALSE       c
#> 3: 2 -9.088870 FALSE       b
``````

Generate LHS Design:

``````requireNamespace("lhs")
generate_design_lhs(ps, 3)
#> <Design> with 3 rows:
#>    z         x  flag methods
#> 1: 1 -3.984673  TRUE       b
#> 2: 2  7.938035 FALSE       a
#> 3: 3  1.969783  TRUE       c
``````

Generate Grid Design:

``````generate_design_grid(ps, resolution = 2)
#> <Design> with 24 rows:
#>     z   x  flag methods
#>  1: 1 -10  TRUE       a
#>  2: 1 -10  TRUE       b
#>  3: 1 -10  TRUE       c
#>  4: 1 -10 FALSE       a
#>  5: 1 -10 FALSE       b
#>  6: 1 -10 FALSE       c
#>  7: 1  10  TRUE       a
#>  [ reached getOption("max.print") -- omitted 18 rows ]
``````

Properties of the parameters within the `ParamSet`:

``````ps\$ids()
#> [1] "z"       "x"       "flag"    "methods"
ps\$levels
#> \$z
#> NULL
#>
#> \$x
#> NULL
#>
#> \$flag
#> [1]  TRUE FALSE
#>
#> \$methods
#> [1] "a" "b" "c"
ps\$nlevels
#>       z       x    flag methods
#>       3     Inf       2       3
ps\$is_number
#>       z       x    flag methods
#>    TRUE    TRUE   FALSE   FALSE
ps\$lower
#>       z       x    flag methods
#>       1     -10      NA      NA
ps\$upper
#>       z       x    flag methods
#>       3      10      NA      NA
``````

### Parameter Checks

Check that a parameter satisfies all conditions of a `ParamSet`, using `\$test()` (returns `FALSE` on mismatch), `\$check()` (returns error description on mismatch), and `\$assert()` (throws error on mismatch):

``````ps\$test(list(z = 1, x = 1))
#> [1] TRUE
ps\$test(list(z = -1, x = 1))
#> [1] FALSE
ps\$check(list(z = -1, x = 1))
#> [1] "z: Element 1 is not >= 1"
ps\$assert(list(z = -1, x = 1))
#> Error in ps\$assert(list(z = -1, x = 1)): Assertion on 'list(z = -1, x = 1)' failed: z: Element 1 is not >= 1.
``````

### Transformations

Transformations are functions with a fixed signature.

• `x` A named list of parameter values
• `param_set` the `ParamSet` used to create the design

Transformations can be used to change the distributions of sampled parameters. For example, to sample values between \$2^-3\$ and \$2^3\$ in a \$log_2\$-uniform distribution, one can sample uniformly between -3 and 3 and exponentiate the random value inside the transformation.

``````ps = ParamSet\$new(
params = list(
ParamInt\$new(id = "z", lower = -3, upper = 3),
ParamDbl\$new(id = "x", lower = 0, upper = 1)
)
)
ps\$trafo = function(x, param_set) {
x\$z = 2^x\$z
return(x)
}
ps_smplr = SamplerUnif\$new(ps)
x = ps_smplr\$sample(2)
xst = x\$transpose()
xst
#> [[1]]
#> [[1]]\$z
#> [1] 0.125
#>
#> [[1]]\$x
#> [1] 0.4137243
#>
#>
#> [[2]]
#> [[2]]\$z
#> [1] 0.5
#>
#> [[2]]\$x
#> [1] 0.3688455
``````

Further documentation can be found in the mlr3book.

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paradox documentation built on Nov. 21, 2022, 5:07 p.m.