Usage steps:　

(1) The R project website for free download is http://www.r-project.org

(2) R project is free to download at following URLs. Choose one of links
      which closes to your location.

(3) Based on operation system, you can choose Linux, MacOS X or Windows.

(4) For example, download for Windows and the first time to install R

(5) Download the R-code (F81.txt, F84.txt, HKY85.txt, TN93.txt) from
      http://www.stat.nctu.edu.tw/hwang/Variance.htm　

(6) Download data example from
      http://www.stat.nctu.edu.tw/hwang/Variance.htm　

(7) Open the R program 　

(8) Before you run the R-code (F81.txt, F84.txt, HKY85.txt, TN93.txt),
      you need to install R packages.The following are the steps to install R packages.
      1. Choose “Packages” and “Install package(s)…”.

　    2. And then choose your country.

      3. Now choose which package you want to install. And in this
          example you need to install the package “seqinr”.　

(9) Now we use F81.txt for the example. And the processes for the other
      three R-codes are the same. Type ”source("D:/F81.txt") “ on R window.
      In parentheses you can change the route where you save the R-code (F81.txt).

(10) Load the data of the two sequences and set the name for them.

(11)  F81 is a function with two parameters (seq1, seq2), which is in the
         form of “F81 ( seq1, seq2)”. "seq1" and "seq2" are the read data of the
         two sequences, such as x1 and x2 in step 10.