Select Odd and Even Rows and Columns from DataFrame in R
In this article, we will discuss how to select odd and even rows from a dataframe in R programming language.
Getting Odd Rows from the Data Frame
The number of rows in a data frame in R can be fetched by the nrow() method. It returns the number of rows in the data frame. The seq_len() method is then applied to generate the integers beginning with 1 to the number of rows. The modulo method with the integer 2 in R can be used to fetch the odd or even rows based on their indexes on the obtained vector. The corresponding row indices of the data frame are operated with a modulo method. The following syntax is used to fetch the odd rows of the data frame.
Syntax:
seq_len(rows)%%2
Data frame indexing method can then be used to obtain rows where the odd row index is equivalent to 1.
Syntax:
data_frame[odd_row == 1, ]
Example: Select odd rows from dataframe
R
# creating a data frame in Rdata_frame <- data.frame(col1 = 1:10, col2 = letters[1:10], col3 = rep(5:9,2)) print ("Original Dataframe")print(data_frame) # getting number of rows in Rrows <- nrow(data_frame) # extracting odd rows odd_rows <- seq_len(rows) %% 2 # getting data from odd data framedata_mod <- data_frame[odd_rows == 1, ] print ("odd rows of dataframe")print(data_mod) |
Output:
[1] "Original Dataframe" col1 col2 col3 1 1 a 5 2 2 b 6 3 3 c 7 4 4 d 8 5 5 e 9 6 6 f 5 7 7 g 6 8 8 h 7 9 9 i 8 10 10 j 9 [1] "odd rows of dataframe" col1 col2 col3 1 1 a 5 3 3 c 7 5 5 e 9 7 7 g 6 9 9 i 8
Getting Even Rows from the Data Frame
The number of rows in a data frame in R can be fetched by the nrow() method. It returns the number of rows in the data frame. The seq_len() method is then applied to generate the integers beginning with 1 to the number of rows. The modulo method with the integer 2 in R can be used to fetch the odd or even rows based on their indexes on the obtained vector. The corresponding row indices of the data frame are operated with a modulo method. The following syntax is used to fetch the odd rows of the data frame.
Syntax:
seq_len(rows)%%2
Data frame indexing method can then be used to obtain rows where the even row index is equivalent to 0.
Syntax:
data_frame[odd_row == 0, ]
Example: Select even rows from dataframe
R
# creating a data frame in Rdata_frame <- data.frame(col1 = 1:10, col2 = letters[1:10], col3 = rep(5:9,2)) print ("Original Dataframe")print(data_frame) # getting number of rows in Rrows <- nrow(data_frame) # extracting odd rows even_rows <- seq_len(rows) %% 2 # getting data from odd data framedata_mod <- data_frame[even_rows == 0, ] print ("even rows of dataframe")print(data_mod) |
Output:
[1] "Original Dataframe" col1 col2 col3 1 1 a 5 2 2 b 6 3 3 c 7 4 4 d 8 5 5 e 9 6 6 f 5 7 7 g 6 8 8 h 7 9 9 i 8 10 10 j 9 [1] "even rows of dataframe" > print(data_mod) col1 col2 col3 2 2 b 6 4 4 d 8 6 6 f 5 8 8 h 7 10 10 j 9
Getting Odd Columns from the Data Frame
The number of columns in a data frame in R can be fetched by the ncol() method. It returns the number of columns in the data frame. The modulo method can then be used with the integer 2 in R can be used to fetch the odd or even columns based on their indexes on the obtained vector. The corresponding column indices of the data frame are operated with a modulo method. The following syntax is used to fetch the odd rows of the data frame.
Syntax:
seq_len(cols)%%2
Data frame indexing method can then be used to obtain rows where the odd column index is equivalent to 1.
Syntax:
Data_frame[, odd_cols==1 ]
Example: select odd columns from dataframe
R
# creating a data frame in Rdata_frame <- data.frame(col1 = 1:10, col2 = letters[1:10], col3 = rep(5:9,2)) print ("Original Dataframe")print(data_frame) # getting number of columns in Rcols <- ncol(data_frame) # extracting odd rows odd_cols <- seq_len(cols) %% 2 # getting data from odd data framedata_mod <- data_frame[, odd_cols == 1] print ("odd columns of dataframe")print(data_mod) |
Output:
[1] "Original Dataframe" col1 col2 col3 1 1 a 5 2 2 b 6 3 3 c 7 4 4 d 8 5 5 e 9 6 6 f 5 7 7 g 6 8 8 h 7 9 9 i 8 10 10 j 9 [1] "odd rows of dataframe" col1 col3 1 1 5 2 2 6 3 3 7 4 4 8 5 5 9 6 6 5 7 7 6 8 8 7 9 9 8 10 10 9
Getting Even Columns from the Data Frame
The number of columns in a data frame in R can be fetched by the ncol() method. It returns the number of columns in the data frame. The modulo method can then be used with the integer 2 in R can be used to fetch the odd or even columns based on their indexes on the obtained vector. The corresponding column indices of the data frame are operated with a modulo method. The following syntax is used to fetch the odd rows of the data frame.
Syntax:
seq_len(cols)%%2
Data frame indexing method can then be used to obtain rows where the odd column index is equivalent to 0.
Syntax:
Data_frame[, odd_cols==0 ]
Example: select even columns from dataframe
R
# creating a data frame in Rdata_frame <- data.frame(col1 = 1:10, col2 = letters[1:10], col3 = rep(5:9,2)) print ("Original Dataframe")print(data_frame) # getting number of columns in Rcols <- ncol(data_frame) # extracting odd rows even_cols <- seq_len(cols) %% 2 # getting data from odd data framedata_mod <- data_frame[, even_cols == 0] print ("even columns of dataframe")print(data_mod) |
Output:
[1] "Original Dataframe" col1 col2 col3 1 1 a 5 2 2 b 6 3 3 c 7 4 4 d 8 5 5 e 9 6 6 f 5 7 7 g 6 8 8 h 7 9 9 i 8 10 10 j 9 [1] "even columns of dataframe" [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j"
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