e variable names.


```r
&gt; #readable, informative code:
&gt; tD[tD$change &gt; 0, "change"] &lt;- NA
&gt; 
&gt; # Indexing by numbers easily becomes 
&gt; # a source of error by itself:
&gt; tD[tD$change &gt; 0, 4] &lt;- NA
```

---

background-image: url(pics/structure.png)
background-size: 30%
background-position: right


## Finishing up after cleaning

Should now have&lt;br&gt;
a cleaned dataset&lt;br&gt;
that can form the&lt;br&gt;
basis for future&lt;br&gt;
analyses.&lt;br&gt;

With documentation&lt