Dynamic Stata Code Block Options

When you include dynamic Stata code in a Markdown document, you do not have to show your reader all the code you use. Just what is visible to your reader is controlled by code block attributes. This optional specification is made as part of the code fence, after the language specification and a comma.

You have the option of showing the reader:

only the output from your code (no commands)
only the code but not the output (perhaps you use stored results, later)
neither code nor output (yet the code needs to be evaluated)

You also have the option of showing the reader:

unevaluated code
suppressing the dot-prompt in code that is shown

See also help dynamic tags##code in Stata Help. When processing your dynamic document using knitr in R, these attributes are referred to as "chunk options".

Most of these options can be specified using the same keywords that are used in Stata's dynamic tags. For compatability, most of these options also have a knitr style of specification or a markstat style of specification.

Examples

Output Only, No Commands

You can show your reader only the output from a code chunk with the nocommands option in the code fence info tag. The knitr version of this option is echo=FALSE.

Your code block looks like this:

```{stata, nocommands}
sysuse auto, clear
tabstat weight, stat(mean sd)
```

But the result in your document is just:

(1978 Automobile Data)


    variable |      mean        sd
-------------+--------------------
      weight |  3019.459  777.1936
----------------------------------

Again, the code block:

```{stata, echo=FALSE}
tabulate foreign
```

And the result in your document:


   Car type |      Freq.     Percent        Cum.
------------+-----------------------------------
   Domestic |         52       70.27       70.27
    Foreign |         22       29.73      100.00
------------+-----------------------------------
      Total |         74      100.00

Code block:

```s, nocommands
pwcorr mpg weight disp
```

What appears in your document:


             |      mpg   weight displa~t
-------------+---------------------------
         mpg |   1.0000 
      weight |  -0.8072   1.0000 
displacement |  -0.7056   0.8949   1.0000

Code Only, No Output

You can show your reader only the code you use, without the output, yet the code is evaluated. Notice that this suppresses all output in your Stata results viewer, as well as in your document. This suppresses the notes that many commands make, but not error messages (which cause your document to simply stop processing, unless you have used the nostop option with stmd for your whole document).

Code block:

```{stata, nooutput}
sysuse auto, clear
regress mpg weight
```

In your document:

. sysuse auto, clear // no dataset note

. regress mpg weight // no output

You might use this is you want to discuss how to write some code, and then later deal with the output.


      Source |       SS           df       MS      Number of obs   =        74
-------------+----------------------------------   F(1, 72)        =    134.62
       Model |   1591.9902         1   1591.9902   Prob > F        =    0.0000
    Residual |  851.469256        72  11.8259619   R-squared       =    0.6515
-------------+----------------------------------   Adj R-squared   =    0.6467
       Total |  2443.45946        73  33.4720474   Root MSE        =    3.4389

------------------------------------------------------------------------------
         mpg |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
      weight |  -.0060087   .0005179   -11.60   0.000    -.0070411   -.0049763
       _cons |   39.44028   1.614003    24.44   0.000     36.22283    42.65774
------------------------------------------------------------------------------

This may also be specified in the knitr manner with results=FALSE or results="hide" (note the capitalization and the quotes).

Neither Code nor Output

To have code evaluated in the background, use the quietly option.

Code block:

```{stata, quietly}
generate gpm=1/mpg
```

(Although I show you my code here, including the code fence, the actual execution takes place quietly after this paragraph.)

In your document:

This is equivalent to using both nocommands and nooutput.

Code block:

```{stata, nocommands, nooutput}
regress gpm weight
```

In your document:

(The markstat style of specification uses a forward slash at the end of the language specification.)

. regress

      Source |       SS           df       MS      Number of obs   =        74
-------------+----------------------------------   F(1, 72)        =    194.71
       Model |  .008729651         1  .008729651   Prob > F        =    0.0000
    Residual |  .003227977        72  .000044833   R-squared       =    0.7300
-------------+----------------------------------   Adj R-squared   =    0.7263
       Total |  .011957628        73  .000163803   Root MSE        =     .0067

------------------------------------------------------------------------------
         gpm |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
      weight |   .0000141   1.01e-06    13.95   0.000     .0000121    .0000161
       _cons |   .0077077   .0031426     2.45   0.017     .0014431    .0139723
------------------------------------------------------------------------------