Data Frames in R: Create, Inspect and Use

A data frame in R is a list of variables that all have the same number of rows, stored with the class “data.frame”. Its columns can be of different types (numeric, logical, factor, character), which is why it is the usual container for a research dataset: one row per observation, one column per variable. This guide covers what R’s own documentation says a data frame is, how to create and inspect one, and the version-specific behaviours that older tutorials still get wrong.

What a data frame is used for in research

The R manual states that a data frame is a list with class “data.frame”, and the data.frame help page calls the result a matrix-like structure “whose columns may be of differing types”. The same page says data frames are “used as the fundamental data structure by most of R’s modeling software”. In practice that means the table you load from a survey export, an instrument file or a spreadsheet is a data frame before you summarise, plot or model it. See what R is used for for the wider picture.

R programming data frame versus a matrix

The manual notes that a data frame can for many purposes be regarded as a matrix with columns of possibly differing modes and attributes. A matrix holds one type throughout; a data frame lets a numeric measurement sit next to a character participant label.

Install or access (official source only)

Data frames are part of base R, so there is nothing extra to install: download R from the Comprehensive R Archive Network (CRAN) at cran.r-project.org. If you prefer an editor, RStudio works with the same commands. The tibble package, a variant of the data frame, is installed from CRAN with:

install.packages("tibble")

Step-by-step: create and inspect a data frame

Data frame in R programming: building one with data.frame()

1. Create one vector per variable, all the same length (or a length that divides evenly into the longest, see Troubleshooting).
2. Pass the vectors to data.frame(), naming each column:

   trial <- data.frame(
     id = 1:4,
     group = c("control", "treated", "control", "treated"),
     score = c(12.5, 14.1, 11.8, 15.3)
   )

3. Look at the first rows with head(trial). Per the utils help page, head() and tail() return the first or last parts of a data frame, and the default is n = 6.
4. Check the shape with nrow(trial) and ncol(trial), which return the number of rows and columns.
5. Inspect the structure with str(trial), which the R manual describes as a compact display of the internal structure of an object, with an S3 method for data frames.

Reading a data frame from a file

The R introduction says the simplest way to construct a data frame from scratch is to read it from a file with read.table(), which reads an entire data frame from an external file. read.csv() is the comma-separated variant with the same result type, a data frame; read.csv2() covers the semicolon-separated variant used where a comma is the decimal mark. A worked file-import walkthrough is in how to load data into R.

Selecting a column

Because a data frame is a list, its components are reached the way list components are: trial$score or trial[["score"]]. The manual notes that Lst$name is the same as Lst[["name"]], and that the double-bracket form is the one to use when the name is held in a variable.

Output and how to read it

Printing a data frame, or its first rows with head(), shows a table: the column names across the top and one row per observation, with an automatic row label at the left. When you do not supply row names, R takes them from the first component with suitable names, and otherwise uses the integers from 1; the help page calls those “automatic”. For summary figures per column, continue with summary statistics in R, and to add columns see cbind in R.

Troubleshooting

Columns of different lengths

The manual requires that vector variables in a data frame all have the same length, and that matrix variables have the same number of rows. The help page adds that atomic vectors, factors and protected character vectors are recycled a whole number of times if necessary, so a length-2 column can fill a length-4 frame but a length-3 column cannot. Fix the shorter vector before building the frame.

Column names that change

With check.names = TRUE (the default), names are checked to be syntactically valid and not duplicated, and are adjusted with make.names if necessary. A header such as a name containing a space is therefore altered on the way in. Set check.names = FALSE to keep it, but note the help page warns that not all operations preserve duplicated names.

Text turning into factors (or not)

The default for stringsAsFactors is FALSE. The help page records that the earlier “factory-fresh” default was TRUE and “has been changed to FALSE for R 4.0.0”. Tutorials written before that release may show character columns arriving as factors; on current R they arrive as character unless you ask for factors.

Free alternatives

Option	What the official documentation says	Where it comes from
Base R data.frame	Tightly coupled collections of variables; matrix-like, columns of differing types	Included with R (CRAN)
read.table() / read.csv()	Reads a file in table format and creates a data frame from it	Included with R (utils package)
tibble	Data frames that are “lazy and surly”: they do less, do not change variable names or types, and do not do partial matching. as_tibble() converts an existing object; tibble() builds one from columns	install.packages("tibble")

For reproducible work, the practical difference is that a tibble does not rename or retype your columns on creation, whereas data.frame() applies the check.names rule above. If you are comparing R with other statistics tools, see SPSS vs R.

FAQ

What is a data frame in R programming?

It is a list of variables with the same number of rows and the class “data.frame”, usually displayed as a table whose columns may hold different types.

How do I create a data frame in R?

Call data.frame() with one named vector per column, or read a file with read.table() or read.csv().

Is a data frame the same as a list?

A data frame is a list with an added class and the restriction that its components be same-length vectors (or matching-row matrices, lists or data frames), so list-style access with $ and [[ ]] works on it.

How many rows does head() show?

Six by default (n = 6), for a data frame as for a vector or matrix.

What is the difference between a data frame and a tibble?

A tibble is a data frame that, per the tibble documentation, does less: it does not change variable names or types and does not do partial matching.

Sources (official docs)

• An Introduction to R, section 6.3 “Data frames” (CRAN, manual for R 4.6.1), checked 2026-10-29.
• R documentation: data.frame (base), checked 2026-10-29.
• R documentation: head (utils), str (utils), read.table (utils) and nrow (base), checked 2026-10-29.
• tibble package documentation (tidyverse), checked 2026-10-29.