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Update relational-data.Rmd #255

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6 changes: 3 additions & 3 deletions relational-data.Rmd
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Expand Up @@ -16,7 16,7 @@ To work with relational data you need verbs that work with pairs of tables. Ther

* __Set operations__, which treat observations as if they were set elements.

The most common place to find relational data is in a _relational_ database management system (or RDBMS), a term that encompasses almost all modern databases. If you've used a database before, you've almost certainly used SQL. If so, you should find the concepts in this chapter familiar, although their expression in dplyr is a little different. Generally, dplyr is a little easier to use than SQL because dplyr is specialised to data analysis: it makes common data analysis operations easier, at the expense of making it more difficult to do other things that don't commonly need for data analysis.
The most common place to find relational data is in a _relational_ database management system (or RDBMS), a term that encompasses almost all modern databases. If you've used a database before, you've almost certainly used SQL. If so, you should find the concepts in this chapter familiar, although their expression in dplyr is a little different. Generally, dplyr is a little easier to use than SQL because dplyr is specialised to do data analysis: it makes common data analysis operations easier, at the expense of making it more difficult to do other things that don't commonly need for data analysis.

### Prerequisites

Expand Down Expand Up @@ -176,7 176,7 @@ flights2 <- flights %>%
flights2
```

(Remember, when you're in RStudio, you can also use `View()` to avoid this problem).
(Remember, when you're in RStudio, you can also use `View()` to avoid this problem.)

Imagine you want to add the full airline name to the `flights2` data. You can combine the `airlines` and `flights2` data frames with `left_join()`:

Expand All @@ -186,7 186,7 @@ flights2 %>%
left_join(airlines, by = "carrier")
```

The result of joining airlines to flights is an additional variable: `name`. This is why I call this type of join a mutating join. In this case, you could have got to the same place using `mutate()` and R's base subsetting:
The result of joining airlines to flights2 is an additional variable: `name`. This is why I call this type of join a mutating join. In this case, you could have got to the same place using `mutate()` and R's base subsetting:

```{r}
flights2 %>%
Expand Down