Exercise

# Logicals and subset()

Here's a fun problem. You know how to create logical vectors that tell you when a certain condition is true, but can you subset a data frame to only contains rows where that condition is true?

If you took *Introduction to R for Finance*, you might remember the `subset()`

function. `subset()`

takes as arguments a data frame (or vector/matrix) and a logical vector of which rows to return:

```
stocks
date ibm panera
1 2017-01-20 170.55 216.65
2 2017-01-23 171.03 216.06
3 2017-01-24 175.90 213.55
4 2017-01-25 178.29 212.22
subset(stocks, ibm < 175)
date ibm panera
1 2017-01-20 170.55 216.65
2 2017-01-23 171.03 216.06
```

Useful, right?

Instructions

**100 XP**

`stocks`

is in your workspace.

- Subset
`stocks`

to include rows where`panera`

is greater than`216`

. - Subset
`stocks`

to retrieve the row where`date`

is equal to`"2017-01-23"`

. Don't forget`as.Date()`

! - Subset
`stocks`

to retrieve rows where`ibm`

is less than`175`

and`panera`

is less than`216.50`

.