Extract given rows and columns from a given dataframe in R

Extraction of given rows and columns has always been one of the most important tasks which are especially required while working on data cleaning activities. In this article, we will be discussing all the sets of commands which are used to extract given rows and columns from a given dataframe in the R programming language.

Extraction of a single element from a dataframe

A single element can be extracted if the exact position of the item is known and is passed.

Syntax: 

df[ row , column ]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[3,2]

Output:

[1] 130

Extraction of given Rows and Columns

Method 1: Extraction of all rows and columns

If no row and column number is specified, all rows and columns basically the complete data set is printed.

Syntax: 

 df[ ,]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[,]

Output:

  c1  c2  c3

1 30 110 280

2 40 120 285

3 50 130 290

Method 2: Extraction of All rows of a column

If no row number is specified, but the column number is set to the required column value, all rows of a column can be extracted.

Syntax:

df[,n]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[,1]

Output:

[1] 30 40 50

Method 3: extraction of All columns of a row

If row number is specified, but no column number is given, all columns of a row can be extracted.

Syntax:

df[n,]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[1,]

Output:

  c1  c2  c3

1 30 110 280

Method 4: extraction of more than one rows with all columns

c in c() means ‘combine’. c function is a generic function which combines it arguments to form vectors. When row numbers to be extracted are specified and column number is not specified, selected rows with all columns are displayed.

Syntax:

df[ c(n,m), ]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[ c(1,3),]

Output:

  c1  c2  c3

1 30 110 280

3 50 130 290

Method 5: extraction of more than one column with all rows

For this number of rows to be extracted should be given with no arguments for rows.

Syntax:

df[,c(n,m)]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[,c(2,3)]

Output:

   c2  c3

1 110 280

2 120 285

3 130 290

Method 6: extraction of range of rows with all columns

If the range is specified for rows with no value for columns, this functionality can be achieved.

Syntax:

df[n:m,]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[1:2,]

Output:

  c1  c2  c3

1 30 110 280

2 40 120 285

Method 7: extraction of a specific row from a range of columns

If the row is provided with the number of the row to be extracted and column with the range our functionality can be achieved.

Syntax:

df[r,n:m]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[2,1:3]

Output:

  c1  c2  c3

2 40 120 285

Method 8: extraction of range of rows and columns

Supply rows and columns with ranges.

Syntax:

df[p:q, n:m]

Example:

R

df <- data.frame( c( 30, 40, 50), c( 110, 120, 130 ),c( 280, 285,290))

names(df) <- c("c1", "c2", "c3")

df[1:2, 1:3]

Output:

    c1  c2  c3

1 30 110 280

2 40 120 285