Factor levels in R Programming - Step-by-Step Execution

Concept Flow - Factor levels

Create vector with values

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Convert vector to factor

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Assign levels automatically

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Use levels for ordering or grouping

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Access or modify levels if needed

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Use factor in analysis or plots

Start with a vector, convert it to a factor which assigns levels automatically, then use or modify these levels for grouping or ordering.

Execution Sample

R Programming

x <- c("apple", "banana", "apple", "cherry")
f <- factor(x)
levels(f)
print(f)

Create a character vector, convert it to a factor, check its levels, and print the factor showing values as levels.

Execution Table

Step	Action	Variable	Value/Result	Notes
1	Create vector x	x	["apple", "banana", "apple", "cherry"]	Vector with repeated fruits
2	Convert x to factor f	f	Factor with levels: apple, banana, cherry	Levels assigned alphabetically by default
3	Check levels of f	levels(f)	["apple", "banana", "cherry"]	Shows unique sorted levels
4	Print factor f	f	[1, 2, 1, 3]	Values shown as factor level codes
5	End			Execution complete

💡 All steps executed; factor created with levels assigned automatically.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
x	undefined	["apple", "banana", "apple", "cherry"]	["apple", "banana", "apple", "cherry"]	["apple", "banana", "apple", "cherry"]
f	undefined	undefined	Factor with levels: apple, banana, cherry	Factor with levels: apple, banana, cherry

Key Moments - 2 Insights

Why does the factor have levels sorted alphabetically, not in the order of appearance?

By default, R assigns factor levels in alphabetical order as shown in step 2 and 3 of the execution_table.

What does printing a factor show compared to printing a character vector?

Printing a factor shows the underlying integer codes representing the factor levels, not just raw strings, as seen in step 4 of the execution_table.

Visual Quiz - 3 Questions

Look at the execution_table, what are the levels of factor f after step 2?

A ["apple", "cherry", "banana"]

B ["banana", "apple", "cherry"]

C ["apple", "banana", "cherry"]

D ["cherry", "banana", "apple"]

💡 Hint

Check the 'Value/Result' column in row for step 2 in execution_table.

At which step is the factor f created from vector x?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' column to find when conversion to factor happens.

If the vector x had values c("banana", "apple", "banana"), how would the levels be ordered by default?

A ["apple", "banana"]

B ["banana", "apple"]

C ["banana"]

D ["apple"]

💡 Hint

Remember factor levels are sorted alphabetically by default as shown in execution_table step 2.

Concept Snapshot

Factor levels in R:
- Create a vector of values
- Convert to factor with factor()
- Levels assigned alphabetically by default
- Use levels() to see or modify levels
- Factors help group and order categorical data

Full Transcript

This example shows how to create a factor in R from a character vector. First, a vector x with fruit names is created. Then, x is converted to a factor f. R automatically assigns levels to f in alphabetical order: apple, banana, cherry. Using levels(f) shows these levels. Printing f displays the underlying integer codes representing the factor levels. Factors are useful for grouping and ordering categories in data analysis.