Join Multiple Dataframes In R

Combine Data Frames in R

  1. Join Multiple Dataframes In R Tutorial
  2. R Merge Dataframe
  3. Combining Multiple Data Frames In R

Append/Join two reactive dataframes (R) shiny. July 17, 2018, 10:22pm #1. I have two reactive dataframes which I am trying to append. While I do so I get. One solution is to use dplyr package and it's innerjoin as follows: library (dplyr) df join (df1, df2) df join (df, df3). R Combine Data Frames – Merge based on a common column (s) merge function is used to merge data frames. The syntax of merge function is: merge(x, y, by, by.x, by.y, sort = TRUE).

Merge is a generic function whose principal method is for data frames: the default method coerces its arguments to data frames and calls the 'data.frame' method. By default the data frames are merged on the columns with names they both have, but separate specifications of the columns can be given by by.x and by.y. In R, the merge command is a great way to match two data frames together. Just read the two data frames into R mydata1 = read.csv (path1, header=T) mydata2 = read.csv (path2, header=T).

In this tutorial, we will learn how to merge or combine two data frames in R programming.

Two R data frames can be combined with respect to columns or rows. We will look into both of these ways.

  • To combine data frames based on a common column(s), i.e., adding columns of second data frame to the first data frame with respect to a common column(s), you can use merge() function.
  • To combine data frames: with rows of second data frame added to those of the first one, you can use rbind() function.

R Combine Data Frames – Merge based on a common column(s)

merge() function is used to merge data frames. The syntax of merge() function is:

where

  • x, y are data frames, or objects to be coerced or combined to one
  • by, by.x, by.y are specifcations of the common columns.
  • sort logical (TRUE or FALSE). Results are sorted on the by columns if TRUE and not if FALSE.

Join Multiple Dataframes In R Tutorial

Dataframes

Example 1 – Combine Data Frames in R using merge()

Combine

In this example, we take two data frames. The first data frame contains id and name of students. The second data frame contains id and marks of students.

You can combine these two data frames with respect to the common column id using merge() function.

The second data frame is added to the first data frame based on a column. The result is a new data frame with new columns.

This is useful when you collect the experimental data from different sources pertaining to the same experiments. Data from a source contains data collected for certain features while other source collects data for other features. Now, using merge(), you can combine these data to get a single data frame containing all the features values of experiments.

R Combine Data Frames – Concatenate Rows of Data Frame to another Data Frame

Join multiple dataframes in r software

rbind() function is used to concatenate data frames. The syntax of rbind() function is:

where

JoinJoin
  • x an R6Frame
  • ... additional parameters sent to rbind

Example 2 – Combine Data Frames in R using rbind()

In this example, we take two data frames. The first data frame contains id and name of students. The second data frame also contains id and name of students. Consider that these are two batches of students and we would like to concatenate these.

You can combine these two data frames with respect to rows using rbind() function.

The rows of second data frame are added to that of first data frame. The result is a new data frame with increased number of rows.

Conclusion

R Merge Dataframe

In this R Tutorial, we have learned how to combine R Data Frames based on rows or columns.

Recipe Objective

In formation of a database, all the data cannot be stored in one table to avoid duplicacy. To extract specific information out of the database, we merge two or more tables using a common field. The merging takes place w.r.t the concept of joins. There are 5 types of joins: ​

  1. Inner join: Returns only matching records
  2. Outer join: Returns all records including no matches in both directions
  3. Left Join: Returns all records in left dataframe and only matching records from the other
  4. Right Join : Returns all records in right dataframe and only matching records from the other
  5. Cross join: Returns all the possible combination of records in both the dataframes

To merge 2 dataframes in R, we use merge() function to do so. In this recipe, we will learn how to merge two dataframe in R using an example.

Step 1: Loading required library and creating 2 dataframes.

Taking an example of university database with 1 table to be of personal details and the other as courses enrolled

#Data manipulation library(tidyverse) # Dataframe 1: personal_details = data.frame(Student_ID = c(1:5), Name = c('Siddhi', 'Jessica', 'Nisarg', 'Vishal', 'Fredo'), Address = c('Mumbai', 'Mumbai', 'Pune', 'Madgaon', 'Nashik')) #Dataframe 2: courses = data.frame(Student_ID = c(2,3,5,8), Course = c('Chemistry', 'Physics', 'Computer Science', 'History')) print(personal_details) print(courses)

Merging the two dataframes

We use the common field 'Student_ID' for merging the data using merge() function. ​

Combining Multiple Data Frames In R

Syntax: merge(x , y, by = , all.x = , all.y = , all = ) ​

where: ​

  1. x = dataframe 1
  2. y = dataframe 2
  3. by = common field by which the merging takes place
  4. all, all.x, all.y = logical values which indicates the type of merge. The default value of all is FALSE(i.e. it returns only the matching rows)

1. Inner Join ​

inner = merge(x=personal_details,y=courses,by='Student_ID') inner

2. Outer Join: (condition: all = TRUE) ​

outer = merge(x=personal_details,y=courses,by='Student_ID', all = TRUE) outer

3. Left Join: (Condition: all.x = TRUE) ​

left = merge(x=personal_details,y=courses,by='Student_ID', all.x = TRUE) left

4. Right Join: (Condition: all.y = TRUE) ​

right = merge(x=personal_details,y=courses,by='Student_ID', all.y = TRUE) right