lmer: how to find the optimal value of one of the explanatory variables that will give the maximum value of the response variable
I am fitting the following model with the lme4 package in R:
lm_noisyBKG_pr2 <- lmer(ranking ~ slope_diff_value_scaled + slope_diff_sign + slope_target_scaled + factor(BKG) * I(slope_target_scaled^2) + (1 | stim_ver), data = df_noisy_lmer, REML = FALSE)