Count number of rows within each group in R DataFrame

Return Column Name of Largest Value for Each Row in R DataFrame

Last Updated : 23 Sep, 2021

In this article, we will discuss how to return column names of the largest value for each row in DataFrame in R Programming Language.

Example:

	Column1	Column2	Column3	Max column
Row1	2	0	0	Column1 , Because, Column2 value and Column 3 value is less than Column1
Row2	4	3	5	Column3 , Because, Column2 value and Column 1 value is less than Column3
Row3	10	6	6	Column1 , Because, Column2 value and Column 3 value is less than Column1
Row4	9	5	4	Column1 , Because, Column2 value and Column 3 value is less than Column1
Row5	7	9	3	Column2 , Because, Column1 value and Column 3 value is less than Column2

So For this implementation we will use colnames() and max.col() functions

Syntax:

colnames(dataframe)[max.col(dataframe)]

Here,

colnames() is used to get the column names
max.col() is used to return the maximum column name of the dataframe

Example: R program to get the largest column name in all rows

R

# create  a dataframe with 3 columns and 3 rows 
data = data.frame(subject1=c(91, 62, 93), 
                  subject2=c(98, 79, 70), 
                  subject3=c(100, 78, 98)) 
  
  
# get the largest column name in each row 
print(colnames(data)[max.col(data)]) 

Output:

[1] "subject3" "subject2" "subject3"

Example: R program to get the largest column name in all rows

R

# create  a dataframe with 4 columns and 3 rows 
data = data.frame(subject1=c(91, 62, 93, 56, 78), 
                  subject2=c(98, 79, 70, 56, 78), 
                  subject3=c(100, 78, 98, 56, 71)) 
  
# get the largest column name in each row 
print(colnames(data)[max.col(data)]) 

Output:

[1] "subject3" "subject1" "subject3" "subject1" "subject2"

Count number of rows within each group in R DataFrame

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