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Import R Data
Revision created 2692 days ago by Abhimanyu Singh-
Import R Data
Revision created 2692 days ago by Abhimanyu Singh
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Import R Data: Revision
It is often necessary to import sample textbook data into R before you start working on your homework.
Excel File
Quite frequently, the sample data is in Excel format, and needs to be imported into R prior to use. For this, we can use the function read.xls from the gdata package. It reads from an Excel spreadsheet and returns a data frame. The following shows how to load an Excel spreadsheet named "mydata.xls". This method requires Perl runtime to be present in the system.
> help(read.xls) # documentation
> mydata = read.xls("mydata.xls") # read from first sheet
Alternatively, we can use the function loadWorkbook from the XLConnect package to read the entire workbook, and then load the worksheets with readWorksheet. The XLConnect package requires Java to be pre-installed.
> wk = loadWorkbook("mydata.xls")
> df = readWorksheet(wk, sheet="Sheet1")
Minitab File
If the data file is in Minitab Portable Worksheet format, it can be opened with the function read.mtp from the foreign package. It returns a list of components in the Minitab worksheet.
> help(read.mtp) # documentation
> mydata = read.mtp("mydata.mtp") # read from .mtp file
SPSS File
For the data files in SPSS format, it can be opened with the function read.spss also from the foreign package. There is a "to.data.frame" option for choosing whether a data frame is to be returned. By default, it returns a list of components instead.
> help(read.spss) # documentation
> mydata = read.spss("myfile", to.data.frame=TRUE)
Table File
A data table can resides in a text file. The cells inside the table are separated by blank characters. Here is an example of a table with 4 rows and 3 columns.
Now copy and paste the table above in a file named "mydata.txt" with a text editor. Then load the data into the workspace with the function read.table.
> mydata # print data frame
V1 V2 V3
1 100 a1 b1
2 200 a2 b2
3 300 a3 b3
4 400 a4 b4
For further detail of the function read.table, please consult the R documentation.
CSV File
The sample data can also be in comma separated values (CSV) format. Each cell inside such data file is separated by a special character, which usually is a comma, although other characters can be used as well.
The first row of the data file should contain the column names instead of the actual data. Here is a sample of the expected format.
After we copy and paste the data above in a file named "mydata.csv" with a text editor, we can read the data with the function read.csv.
> mydata
Col1 Col2 Col3
1 100 a1 b1
2 200 a2 b2
3 300 a3 b3
In various European locales, as the comma character serves as the decimal point, the function read.csv2 should be used instead. For further detail of the read.csv and read.csv2 functions, please consult the R documentation.
Working Directory
Finally, the code samples above assume the data files are located in the R working directory, which can be found with the function getwd.
You can select a different working directory with the function setwd(), and thus avoid entering the full path of the data files.
Note that the forward slash should be used as the path separator even on Windows platform.
