Convert numeric vector to factor [duplicate]

Question

I am trying to convert a set of variables as factored variable : example in variable quality the values are : 3,4,5,6,7,8,9 I want a new FACTORED variable qual_level which has values low , medium and high such that

low <- quality(3,4)
medium<- quality(5,6,7)
high<- quality(8,9)

Hence I tried implementing following code .

q_levels <-  a <- factor (white_wine$quality ,
                      c(3,4,5.6,7,8,9,10), 
                      levels=1:3, 
                      labels=c("Low",  "Medium", "High"))

Above code throws an error :

Error in factor(white_wine$quality, c(3, 4, 5.6, 7, 8, 9, 10), levels = 1:3, : invalid 'labels'; length 3 should be 1 or 2

How can I improve the code ?

Answer 1

Use cut to discretise a continuous variable:

x <- c(3,4,5,6,7,8,9)
cut(x, c(-Inf, 4, 7, 9), labels = c("Low",  "Medium", "High"))
#[1] Low    Low    Medium Medium Medium High   High  
#Levels: Low Medium High

Answer 2

If you have more levels, cut() is the way to go. But, if you have seven levels only, you can also use fct_collapse() in the forcats package.

library(forcats)

quality <- factor(3:9)

fct_collapse(quality,
             low = c("3", "4"),
             medium = c("5", "6", "7"),
             high = c("8", "9"))

#[1] low    low    medium medium medium high   high  
#Levels: low medium high