Table of Contents
Rearranging columns in a data frame is a common task in data analysis. In R, this can be achieved by using the “stack” function which creates a stack structure by stacking the columns on top of each other. This allows for a more organized and efficient view of the data, making it easier to perform further analysis. To rearrange columns in a data frame using the stack function in R, simply specify the desired order of the columns in the function and assign it to a new data frame. This will create a stacked structure with the specified column order, facilitating easier data manipulation and visualization. Overall, rearranging columns using the stack function in R provides a practical and effective solution for data management and organization.
Stack Data Frame Columns in R
Often you may want to stack two or more data frame columns into one column in R.
For example, you may want to go from this:
person trial outcome1 outcome2
A 1 7 4
A 2 6 4
B 1 6 5
B 2 5 5
C 1 4 3
C 2 4 2
To this:
person trial outcomes value
A 1 outcome1 7
A 2 outcome1 6
B 1 outcome1 6
B 2 outcome1 5
C 1 outcome1 4
C 2 outcome1 4
A 1 outcome2 4
A 2 outcome2 4
B 1 outcome2 5
B 2 outcome2 5
C 1 outcome2 3
C 2 outcome2 2
This tutorial explains two methods you can use in R to do this.
Method 1: Use the Stack Function in Base R
The following code shows how to stack columns using the stack function in base R:
#create original data frame data <- data.frame(person=c('A', 'A', 'B', 'B', 'C', 'C'), trial=c(1, 2, 1, 2, 1, 2), outcome1=c(7, 6, 6, 5, 4, 4), outcome2=c(4, 4, 5, 5, 3, 2)) #stack the third and fourth columnscbind(data[1:2], stack(data[3:4])) person trial values ind 1 A 1 7 outcome1 2 A 2 6 outcome1 3 B 1 6 outcome1 4 B 2 5 outcome1 5 C 1 4 outcome1 6 C 2 4 outcome1 7 A 1 4 outcome2 8 A 2 4 outcome2 9 B 1 5 outcome2 10 B 2 5 outcome2 11 C 1 3 outcome2 12 C 2 2 outcome2
Method 2: Use the Melt Function from Reshape2
The following code shows how to stack columns using the melt function from the reshape2 library:
#load library library(reshape2) #create original data frame data <- data.frame(person=c('A', 'A', 'B', 'B', 'C', 'C'), trial=c(1, 2, 1, 2, 1, 2), outcome1=c(7, 6, 6, 5, 4, 4), outcome2=c(4, 4, 5, 5, 3, 2)) #melt columns of data frame melt(data, id.var = c('person', 'trial'), variable.name = 'outcomes') person trial outcomes value 1 A 1 outcome1 7 2 A 2 outcome1 6 3 B 1 outcome1 6 4 B 2 outcome1 5 5 C 1 outcome1 4 6 C 2 outcome1 4 7 A 1 outcome2 4 8 A 2 outcome2 4 9 B 1 outcome2 5 10 B 2 outcome2 5 11 C 1 outcome2 3 12 C 2 outcome2 2
You can find the complete documentation for the melt function here.
Additional Resources
How to Switch Two Columns in R
How to Rename Columns in R
How to Sum Specific Columns in R