course
/
r4ds
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Fix typos (#205)

This commit is contained in:
behrman 2016-07-29 05:48:30 -07:00 committed by Hadley Wickham
parent 1187b85e01
commit 35ba12dfae
1 changed files with 5 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
transform.Rmd
View File

@ -125,7 +125,7 @@ filter(flights, !(arr_delay > 120 | dep_delay > 120))
filter(flights, arr_delay <= 120, dep_delay <= 120)
```
As well as `&` and `|`, R also has `&&` and `||`. Don't use them here! You'll when you should use them in [conditional execution].
As well as `&` and `|`, R also has `&&` and `||`. Don't use them here! You'll learn when you should use them in [conditional execution].
Sometimes you want to find all rows after the first `TRUE`, or all rows until the first `FALSE`. The window functions `cumany()` and `cumall()` allow you to find these values:
@ -309,7 +309,7 @@ select(flights, time_hour, air_time, everything())
vars <- c("year", "month", "day", "dep_delay", "arr_delay")
```
1. Does the result of running the following code suprise you? How do the
1. Does the result of running the following code surprise you? How do the
select helpers deal with case by default? How can you change that default?
```{r, eval = FALSE}
@ -784,7 +784,7 @@ daily <- group_by(flights, year, month, day)
(per_year <- summarise(per_month, flights = sum(flights)))
```
Be careful when progressively rolling up summaries: it's OK for sums and counts, but you need to think about weighting means and variances, and it's not possible to do it exactly for rank-based statistics like the median. In otherwords, the sum of groupwise sums is the overall sum, but the median of groupwise medians is not the overall median.
Be careful when progressively rolling up summaries: it's OK for sums and counts, but you need to think about weighting means and variances, and it's not possible to do it exactly for rank-based statistics like the median. In other words, the sum of groupwise sums is the overall sum, but the median of groupwise medians is not the overall median.
### Ungrouping
@ -814,7 +814,7 @@ daily %>%
Which is more important: arrival delay or departure delay?
1. Our definition of cancelled flights (`!is.na(dep_delay) & !is.na(arr_delay)`
) is slightly sup-optimal. Why? Which is the most important column?
) is slightly suboptimal. Why? Which is the most important column?
1. Look at the number of cancelled flights per day. Is there a pattern?
Is the proportion of cancelled flights related to the average delay?
@ -874,7 +874,7 @@ Functions that work most naturally in grouped mutates and filters are known as
1. Delays are typically temporally correlated: even once the problem that
caused the initial delay has been resolved, later flights are delayed
to allow earlier flights to leave. Using `lag()` explore how the delay
of a flight is related to the delay of the immediately preceeding flight.
of a flight is related to the delay of the immediately preceding flight.
1. Look at each destination. Can you find flights that are suspiciously
fast? (i.e. flights that represent a potential data entry error). Compute