get_modelmatrix() fails for brms models with monotonic effects mo

[DominiqueMakowski]

library(brms)

m <- brm(mpg ~ mo(gear), data = mtcars, refresh=0)

insight::get_modelmatrix(m)
#> Error in model.frame.default(object, data, xlev = xlev): invalid type (list) for variable 'mo(gear)'

^{Created on 2024-07-22 with reprex v2.0.2}

[strengejacke]

library(brms)
#> Loading required package: Rcpp
#> Loading 'brms' package (version 2.21.0). Useful instructions
#> can be found by typing help('brms'). A more detailed introduction
#> to the package is available through vignette('brms_overview').
#> 
#> Attaching package: 'brms'
#> The following object is masked from 'package:stats':
#> 
#>     ar
m <- brm(mpg ~ mo(gear), data = mtcars, refresh=0)
#> Compiling Stan program...
#> Start sampling
insight::get_modelmatrix(m)
#>                     (Intercept) gear
#> Mazda RX4                     1    4
#> Mazda RX4 Wag                 1    4
#> Datsun 710                    1    4
#> Hornet 4 Drive                1    3
#> Hornet Sportabout             1    3
#> Valiant                       1    3
#> Duster 360                    1    3
#> Merc 240D                     1    4
#> Merc 230                      1    4
#> Merc 280                      1    4
#> Merc 280C                     1    4
#> Merc 450SE                    1    3
#> Merc 450SL                    1    3
#> Merc 450SLC                   1    3
#> Cadillac Fleetwood            1    3
#> Lincoln Continental           1    3
#> Chrysler Imperial             1    3
#> Fiat 128                      1    4
#> Honda Civic                   1    4
#> Toyota Corolla                1    4
#> Toyota Corona                 1    3
#> Dodge Challenger              1    3
#> AMC Javelin                   1    3
#> Camaro Z28                    1    3
#> Pontiac Firebird              1    3
#> Fiat X1-9                     1    4
#> Porsche 914-2                 1    5
#> Lotus Europa                  1    5
#> Ford Pantera L                1    5
#> Ferrari Dino                  1    5
#> Maserati Bora                 1    5
#> Volvo 142E                    1    4
#> attr(,"assign")
#> [1] 0 1

^{Created on 2024-07-22 with reprex v2.1.1}