Handling data with CSV files

In this section, we will explain ways in which you can handle files with the Comma-separated Values (CSV) file format.

Getting ready

Install the DataFrames package, which is the Julia package for working with data arrays and dataframes. The command for adding the DataFrames packages to the catalog is as follows:

Pkg.add("DataFrames")

Make sure that all the installed packages are up-to-date: Pkg.update()

How to do it...

CSV files, as the name suggests, are files whose contents are separated by commas. CSV files can be accessed and read into the REPL process by executing the following steps:

1. Assign a variable to the local source directory of the file:

   s = "/Users/username/dir/iris.csv"
   

2. The readtable() command is used to read the data from the source. The data is read in the form of a Julia DataFrame:

   iris = readtable(s)
   

Data can be written to CSV files from a Julia DataFrame using the following steps:

1. Create a data structure with some data inside it. For example, let's create a two-dimensional dataframe to view the the process of writing files of different formats better using DataFrames:

   df = DataFrame(A = 1:10, B = 11:20)
   

   • The preceding command creates a two-dimensional dataframe with columns named A and B.
2. Now, the dataframe created in Step 1 can be exported to an external CSV file by using the following command:

   writetable("data.csv", df)