如何获取R语言中Shapiro-Wilk检验函数shapiro.test的实现代码？

Hey there! I totally get the frustration when you're trying to dig into the actual code behind shapiro.test() and the standard help docs or quick web searches don't give you what you need. Let me walk you through a few solid ways to uncover the implementation details:

• Check the top-level R function code directly
  In your R console, just type shapiro.test and hit enter. This will show you the wrapper code for the function. You'll notice it dispatches to shapiro.test.default for numeric inputs, which is where the real logic starts.

• Retrieve the default method's source code
  Since the core implementation might be hidden in the stats package's namespace, use the getAnywhere() function to pull it up:

  getAnywhere(shapiro.test.default)
  

  This will display the full R code that handles the test setup, calls underlying computational functions, and formats the output.

• Dig into the compiled low-level code
  The heavy lifting of the Shapiro-Wilk test (like calculating the test statistic and p-value) is done in compiled C/Fortran code for performance. To access this:

  1. First, identify the underlying compiled functions called by shapiro.test.default (you'll see references to pshapiro or similar in the R code).
  2. You can view the source code for these by checking the official R source repository's src/library/stats/src directory—look for files like shapiro.c or swilk.f (the Fortran implementation of the Shapiro-Wilk algorithm).
  3. Alternatively, use find("pshapiro") in R to confirm it's a compiled function from the stats package, then cross-reference with the public R source code.

• Step through the function with debugging
  If you want to trace exactly how the test runs, use debugonce(shapiro.test) then run a test call like shapiro.test(rnorm(50)). This will let you step through each line of the function code and see how it interacts with the underlying compiled routines.

内容的提问来源于stack exchange，提问作者Dmitry