Fix contrast-formatting for numerics

[strengejacke]

We couldn't format contrasts that included numerics like we did for factors only, namely two Level columns. This PR fixes this issue and allows proper formatting for numerics as well.

library(lme4)
set.seed(123)

dat <- data.frame(
  outcome = rbinom(n = 100, size = 1, prob = 0.35),
  var_binom = as.factor(rbinom(n = 100, size = 1, prob = 0.2)),
  var_cont = rnorm(n = 100, mean = 10, sd = 7),
  grp = sample(letters[1:4], size = 100, replace = TRUE)
)

dat$var_cont <- datawizard::standardize(dat$var_cont)

m1 <- glmer(
  outcome ~ var_binom + var_cont + (1 | grp),
  data = dat,
  family = binomial(link = "logit")
)

# range of values
modelbased::estimate_contrasts(
  m1,
  c("var_binom", "var_cont"),
  predict = "link",
  transform = exp,
  length = 3
)

## OLD FORMATTING

#> Marginal Contrasts Analysis
#> 
#> Parameter           | Difference |        95% CI |     p
#> --------------------------------------------------------
#> 0 -0.187 - 0 -2.012 |       1.11 | [0.52,  2.39] | 0.791
#> 0  1.638 - 0 -2.012 |       1.23 | [0.27,  5.69] | 0.791
#> 0  3.463 - 0 -2.012 |       1.36 | [0.14, 13.58] | 0.791
#> 1 -2.012 - 0 -2.012 |       1.04 | [0.36,  3.02] | 0.940
#> 1 -0.187 - 0 -2.012 |       1.16 | [0.30,  4.50] | 0.836
#> 1  1.638 - 0 -2.012 |       1.28 | [0.19,  8.87] | 0.802
#> ...

## NEW FORMATTInG

#> Marginal Contrasts Analysis
#> 
#> Level1    | Level2    | Difference |        95% CI |     p
#> ----------------------------------------------------------
#> 0, 0.725  | 0, -2.012 |       1.17 | [0.37,  3.68] | 0.791
#> 0, 3.463  | 0, -2.012 |       1.36 | [0.14, 13.58] | 0.791
#> 1, -2.012 | 0, -2.012 |       1.04 | [0.36,  3.02] | 0.940
#> 1, 0.725  | 0, -2.012 |       1.22 | [0.24,  6.20] | 0.814
#> 1, 3.463  | 0, -2.012 |       1.42 | [0.10, 19.30] | 0.792
#> 0, 3.463  | 0, 0.725  |       1.17 | [0.37,  3.69] | 0.791
#> 1, -2.012 | 0, 0.725  |       0.89 | [0.20,  4.01] | 0.882
#> 1, 0.725  | 0, 0.725  |       1.04 | [0.36,  3.02] | 0.940
#> ...

^{Created on 2025-02-20 with reprex v2.1.1}