Import & Merge Multiple csv Files in R (Example)

In this article, I’ll show you how to import and merge csv files in the R programming language.

The page will contain the following topics:

• Exemplifying Data
• Import & Load csv Files in R
• Video & Further Resources

Let’s do this!

Exemplifying Data

Before we can start with the example, we need to create an exemplifying directory including multiple csv files. First, we need to create several data frames…

data1 <- data.frame(id = 1:6,                                     # Create first example data frame
                    x1 = c(5, 1, 4, 9, 1, 2),
                    x2 = c("A", "Y", "G", "F", "G", "Y"))
 
data2 <- data.frame(id = 4:9,                                     # Create second example data frame
                    y1 = c(3, 3, 4, 1, 2, 9),
                    y2 = c("a", "x", "a", "x", "a", "x"))
 
data3 <- data.frame(id = 5:6,                                     # Create third example data frame
                    z1 = c(3, 2),
                    z2 = c("K", "b"))

…and then we need to export these data frames as csv files to our computer:

write.csv(data1, "C:/...Your Path.../my_folder/data1.csv")        # Write first example data frame
write.csv(data2, "C:/...Your Path.../my_folder/data2.csv")        # Write second example data frame
write.csv(data3, "C:/...Your Path.../my_folder/data3.csv")        # Write third example data frame

Figure 1: Exemplifying Directory with csv Files.

Figure 1 illustrates how our example directory looks like. Now let’s import and combine these data sets in RStudio…

Import & Load csv Files in R

We need three R add-on packages for the following R syntax: dplyr, plyr, and readr. Let’s install and load the packages to R.

install.packages("dplyr")                                         # Install dplyr package
install.packages("plyr")                                          # Install plyr package
install.packages("readr")                                         # Install readr package
 
library("dplyr")                                                  # Load dplyr package
library("plyr")                                                   # Load plyr package
library("readr")                                                  # Load readr package

Now, we can import and merge the example csv files based on the list.files, lapply, read_csv, and bind_rows functions:

data_all <- list.files(path = "C:/...Your Path.../my_folder",     # Identify all csv files in folder
                       pattern = "*.csv", full.names = TRUE) %>% 
  lapply(read_csv) %>%                                            # Store all files in list
  bind_rows                                                       # Combine data sets into one data set 
data_all                                                          # Print data to RStudio console

Table 1: Tibble Containing Three Data Sets.

Table 1 shows the output of the previous R code. As you can see, our three data sets were combined in a single data set. Data set cells were set to NA, in case a variable was not included in all data sets.

Note that our previous R syntax created a tibble instead of a data frame. In case you prefer to work with data frames, you could simply convert this tibble to a data frame as follows:

as.data.frame(data_all)                                           # Convert tibble to data.frame

Video & Further Resources

Have a look at the following video that I have recently released on my Statistics Globe YouTube channel. I illustrate the contents of this article in more detail in the video.

The YouTube video will be added soon.

Please also note that the previous R code merged our data files by just column binding the different data sources to each other. However, it would also be possible to merge our data sets by a shared column name in order to avoid duplicated observations (i.e. our data sets contain an ID column). You could learn more about this type of merging HERE.

In addition, I can recommend to read the other articles on this homepage.

• Read XLSX and XLS Files to R
• The dir Function in R
• Write & Read Multiple CSV Files Using for-Loop
• R Functions List (+ Examples)
• The R Programming Language

On this page I showed you how to combine all csv files in a folder in the R programming language. Let me know in the comments section, in case you have further questions.