Snel parsen met lubridate::fast_strptime

lubridate heeft een eigen snelle datetime-parser: fast_strptime(). In plaats van een order-argument zoals parse_date_time() gebruikt deze een format-argument, en het format moet voldoen aan de strptime()-stijl.

Zoals je in de video zag, betekent dit dat elk teken dat een datum- of tijdonderdeel voorstelt, voorafgegaan moet worden door een % en dat alle niet-witruimtetekens expliciet moeten worden opgenomen.

Probeer dates te parsen met fast_strptime() en vergelijk daarna de snelheid met de andere methoden die je hebt gezien.

Deze oefening maakt deel uit van de cursus

Werken met datums en tijden in R

Cursus bekijken

Oefeninstructies

dates staat weer in je werkruimte.

Bekijk de head van dates. Welke onderdelen zijn aanwezig? Welke scheidingstekens worden gebruikt?
Parse dates met fast_strptime() door de juiste formattekenreeks op te geven.
Vergelijk de timing van fast_strptime() met fasttime en ymd_hms().

Praktische interactieve oefening

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

# Head of dates
head(___)

# Parse dates with fast_strptime
fast_strptime(dates, 
    format = ___) %>% str()

# Comparse speed to ymd_hms() and fasttime
microbenchmark(
  ymd_hms = ymd_hms(dates),
  fasttime = fastPOSIXct(dates),
  fast_strptime = ___(dates, 
    format = ___),
  times = 20)

Code bewerken en uitvoeren

Deze oefening maakt deel uit van de cursus

Werken met datums en tijden in R

SkillTag.level.intermediateSkillTag.label

4.8+

Begin de cursus gratis

R doesn't know something is a date or time unless you tell it. In this chapter you'll learn about some of the ways R stores dates and times by exploring how often R versions are released, and how quickly people download them. You'll also get a sneak peek at what you'll learn in the following chapters.

Exercise 1: Introduction to dates Exercise 2: Recognizing ISO 8601 dates Exercise 3: Specifying dates Exercise 4: Automatic import Exercise 5: Why use dates?Exercise 6: Plotting Exercise 7: Arithmetic and logical operators Exercise 8: What about times?Exercise 9: Getting datetimes into R Exercise 10: Datetimes behave nicely too Exercise 11: Why lubridate?

Dates and times come in a huge assortment of formats, so your first hurdle is often to parse the format you have into an R datetime. This chapter teaches you to import dates and times with the lubridate package. You'll also learn how to extract parts of a datetime. You'll practice by exploring the weather in R's birthplace, Auckland NZ.

Exercise 1: Parsing dates with lubridate Exercise 2: Selecting the right parsing function Exercise 3: Specifying an order with `parse_date_time()`Exercise 4: Weather in Auckland Exercise 5: Import daily weather data Exercise 6: Import hourly weather data Exercise 7: Extracting parts of a datetime Exercise 8: What can you extract?Exercise 9: Adding useful labels Exercise 10: Extracting for plotting Exercise 11: Extracting for filtering and summarizing Exercise 12: Rounding datetimes Exercise 13: Practice rounding Exercise 14: Rounding with the weather data

Getting datetimes into R is just the first step. Now that you know how to parse datetimes, you need to learn how to do calculations with them. In this chapter, you'll learn the different ways of representing spans of time with lubridate and how to leverage them to do arithmetic on datetimes. By the end of the chapter, you'll have calculated how long it's been since the first man stepped on the moon, generated sequences of dates to help schedule reminders, calculated when an eclipse occurs, and explored the reigns of monarch's of England (and which ones might have seen Halley's comet!).

Exercise 1: Taking differences of datetimes Exercise 2: How long has it been?Exercise 3: How many seconds are in a day?Exercise 4: Time spans.Exercise 5: Adding or subtracting a time span to a datetime Exercise 6: Duration or Period?Exercise 7: Arithmetic with timespans Exercise 8: Generating sequences of datetimes Exercise 9: The tricky thing about months Exercise 10: Intervals Exercise 11: Examining intervals. Reigns of kings and queens Exercise 12: Comparing intervals and datetimes Exercise 13: Converting to durations and periods

You now know most of what you need to tackle data that includes dates and times, but there are a few other problems you might encounter in practice. In this final chapter you'll learn a little more about these problems by returning to some of the earlier data examples and learning how to handle time zones, deal with times when you don't care about dates, parse dates quickly, and output dates and times.

Exercise 1: Tijdzones Exercise 2: De tijdzone instellen Exercise 3: Bekijken in een tijdzone Exercise 4: Tijdzones in de weerdata Exercise 5: Tijden zonder datums Exercise 6: Meer over datetimes importeren en exporteren Exercise 7: Snel parsen met fasttime Exercise 8: Snel parsen met lubridate::fast_strptime

Huidige oefening

Exercise 9: Mooie datums en tijden weergeven Exercise 10: Afronding