Create a new Variable of values of another variable-multilevel regression

I am up to create a multilevel analysis (and I am a total newbie).

In this analysis I want to test if a high value of a predictor( here:senseofhumor) (numeric value - transfered into "high","low","medium") would predict the (numeric)outcome more than the other (numeric)predictors (senseofhomor-seriousness-friednlyness). I have a dataset with many people and groups and want to compare the outcome between the groups regarding the influence of SenseofhumorHIGH

The code for that might look like this

RandomslopeEC <- lme(criteria(timepoint1) ~ senseofhumor + seriousness + friendlyness , data = DATA, random = ~ **SenseofhumorHIGH**|group)

For that reason I created values "high" "low" "medium" for my numeric predictor via

library(tidyverse)
DATA <- DATA %>% 
  mutate(predictorNew = case_when(senseofhumor< quantile(senseofhumor, 0.5) ~ 'low', 
                      senseofhumor > quantile(senseofhumor, 0.75)~'high', 
                      TRUE ~ 'med'))

Now they look like this:

Now I realized i might need to cut this variable values in separate variables if I want to test my idea.

Do any of you know how to generate variables, that they may look like this?

Does this make any sense to you regarding my approach? Or do you have a better idea?

Thanks a lot in advance

Welcome to learning R. You will want to convert these types of variables to "factors," and R will be able to process them accordingly. To do that, use as.factor(variable) - so for you it may be DATA$senseofhumor <- as.factor(DATA$senseofhumor). If you need to convert multiple columns, you can use:

factor_cols <- c("Var1","Var2","Var3") # list columns you want as factors
DATA[factor_cols] <- lapply(DATA[factor_cols], as.factor)

Since you are new, note that this forum is typically for questions that cant be easily found online. This question is relatively routine and more details can be found with a quick google search. While SO is a great place to learn R, you may be penalized by the SO community in the future for routine questions like this. Just trying to help ensure you keep learning!