Scanning text files

In previous recipes, we introduced how to use read.table and read.csv to load data into an R session. However, read.table and read.csv only work if the number of columns is fixed and the data size is small. To be more flexible in data processing, we will demonstrate how to use the scan function to read data from the file.

Getting ready

In this recipe, you need to have completed the previous recipes and have snp500.csv downloaded in the current directory.

How to do it…

Please perform the following steps to scan data from the CSV file:

1. First, you can use the scan function to read data from snp500.csv:

   > stock_data3 <- scan('snp500.csv',sep=',', what=list(Date = '', Open = 0, High = 0, Low = 0,Close = 0, Volume = 0, Adj_Close = 0),  skip=1, fill=T)
   Read 16481 records
   

2. You can then examine loaded data with mode and str:

   > mode(stock_data3)
   [1] "list"
   > str(stock_data3)
   List of 7
    $ Date     : chr [1:16481] "2015-07...