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Factor () in R for categorical variables with only hierarchy level?

I am very confused when to use

factor (education) or factor (age group)
 in R. Is it used for categorical ordered data? or can I just use simple categorical data for it without hierarchy?

I know it is that simple. I really need some clarification.

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2 answers

I do not see an unambiguous question here, so perhaps a simple example will be sufficient to answer.

Imagine that we have the following data.

set1 <- c("AA", "B", "BA", "CC", "CA", "AA", "BA", "CC", "CC")

We want to define this data.

f.set1 <- factor(set1)

. , R , , (. "" ).

f.set1
# [1] AA B  BA CC CA AA BA CC CC
# Levels: AA B BA CA CC
is.ordered(f.set1)
# [1] FALSE

as.numeric , . , "5" "4" , table(f.set1) ( , table(set1).

as.numeric(f.set1)
# [1] 1 2 3 5 4 1 3 5 5
table(f.set1)
# f.set1
# AA  B BA CA CC 
#  2  1  2  1  3

, , ordered levels. levels plus ordered = TRUE , , levels ( , ).

o.set1 <- factor(set1, 
                 levels = c("CA", "BA", "AA", "CC", "B"), 
                 ordered = TRUE)

.

o.set1
# [1] AA B  BA CC CA AA BA CC CC
# Levels: CA < BA < AA < CC < B
is.ordered(o.set1)
# [1] TRUE

as.numeric table.

as.numeric(o.set1)
# [1] 3 5 2 4 1 3 2 4 4
table(o.set1)
# o.set1
# CA BA AA CC  B 
#  1  2  2  3  1

, , factor() ; factor() levels ordered = TRUE .

ordered(), . :

ordered(set1, levels = c("CA", "BA", "AA", "CC", "B"))
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, ordered(x) factor(x, ordered=TRUE). "" ?factor , :

, -.

( ), :

f  <- factor(letters[3:1], levels=letters[3:1])
of <- ordered(letters[3:1], levels=letters[3:1])
attributes(f)
# $levels
# [1] "c" "b" "a"
# 
# $class
# [1] "factor"
attributes(of)
# $levels
# [1] "c" "b" "a"
# 
# $class
# [1] "ordered" "factor"

( " " ) is.ordered() "ordered" , , . :

## The print method for factors. (Type 'print.factor' to see the function code)
print(f)
# [1] c b a
# Levels: c b a
print(of)
# [1] c b a
# Levels: c < b < a

## The contrasts function. (Type 'contrasts' to see the function code.)
contrasts(of)
#                 .L         .Q
# [1,] -7.071068e-01  0.4082483
# [2,]  4.350720e-18 -0.8164966
# [3,]  7.071068e-01  0.4082483
contrasts(f)
#   b a
# c 0 0
# b 1 0
# a 0 1
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