R levels() Function - Factor Level Operations
R Language ExampleR levels() function is used to get or set the levels (categories) of a factor.
levels() can be used to view which categories a factor contains, and also to modify category names or reorder them.
The syntax of the levels() function is as follows:
levels(x) levels(x) <- value
Parameter description:
xFactor.
valueNew level vector.
Example
# Create factor
blood_type <- factor(c("A", "B", "AB", "O", "A", "B", "O", "A"))
print("Blood type factor:")
print(blood_type)
print("Levels:")
print(levels(blood_type))
# Frequency count
print("Blood type counts:")
print(table(blood_type))
# Modify level labels
levels(blood_type) <- c("Type A", "Type B", "Type AB", "Type O")
print("After modifying labels:")
print(blood_type)
# Reorder levels (rebuild via factor)
result <- factor(blood_type,
levels = c("Type O", "Type A", "Type B", "Type AB"))
print("In order:")
print(table(result))
blood_type <- factor(c("A", "B", "AB", "O", "A", "B", "O", "A"))
print("Blood type factor:")
print(blood_type)
print("Levels:")
print(levels(blood_type))
# Frequency count
print("Blood type counts:")
print(table(blood_type))
# Modify level labels
levels(blood_type) <- c("Type A", "Type B", "Type AB", "Type O")
print("After modifying labels:")
print(blood_type)
# Reorder levels (rebuild via factor)
result <- factor(blood_type,
levels = c("Type O", "Type A", "Type B", "Type AB"))
print("In order:")
print(table(result))
The output of executing the above code is:
[1] "血型因子:" [1] A B AB O A B O A Levels: A AB B O [1] "水平:" [1] "A" "AB" "B" "O" [1] "各血型数量:" A AB B O 3 1 2 2 [1] "修改标签后:" [1] A型 B型 AB型 O型 A型 B型 O型 A型 Levels: A型 B型 AB型 O型 [1] "按序排列:" O型 A型 B型 AB型 2 3 2 1Other Extensions