3 Linking Code Blocks

3.1 Introduction

By default, the SAS code blocks ("chunks") in an R Markdown document are each run as a separate batch file - they are not connected to each other. However, often we want to write about a sequence of connected steps, interspersing code, results, and explanatory text.

We could simply repeat the necessary code in each code chunk, perhaps hiding part of the code with a selective echo chunk option (a useful technique to know about).

However, it is even simpler to automate this code repetition by using the collectcode chunk option. We simply need to mark those code chunks we need re-executed in subsequent chunks.

3.2 Load SASmarkdown

```{r} 
library(SASmarkdown)
```

3.3 Example: Linking Code Blocks

Suppose your first code block is a DATA step, explaining how to calculate a new variable. Specify the collectcode chunk option to have this DATA step "carry over" in (all of) the following code blocks.

This is written as:

```{sas, collectcode=TRUE} 
data class;
  set sashelp.class;
  bmi = 703*weight/height**2;
run;
```

In your document, the result is:

data class;
  set sashelp.class;
  bmi = 703*weight/height**2;
  run;

Next, we have a separate code block that uses the data. This is just a plain SAS code block.

```{sas} 
proc means data=class;
  var bmi;
run;
```

In your document this is:

proc means data=class;
  var bmi;
  run;

                            The MEANS Procedure

                         Analysis Variable : bmi 
 
     N            Mean         Std Dev         Minimum         Maximum
    ------------------------------------------------------------------
    19      17.8632519       2.0926193      13.4900007      21.4296601
    ------------------------------------------------------------------

Written using

• SASmarkdown version 0.8.0.
• knitr version 1.40.
• R version 4.2.2 (2022-10-31 ucrt).