Parsing veloce con lubridate::fast_strptime

lubridate offre un parser di data-ora veloce: fast_strptime(). Invece di accettare un argomento order come parse_date_time(), accetta un argomento format e il formato deve seguire lo stile di strptime().

Come hai visto nel video, questo significa che ogni carattere che rappresenta un componente di data-ora deve essere preceduto da % e qualsiasi carattere non di spaziatura deve essere incluso esplicitamente.

Prova a fare il parsing di dates con fast_strptime() e poi confronta la sua velocità con gli altri metodi che hai visto.

Questo esercizio fa parte del corso

Lavorare con date e orari in R

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Istruzioni dell'esercizio

dates è di nuovo nel tuo workspace.

Esamina l'intestazione di dates. Quali componenti sono presenti? Quali separatori vengono usati?
Esegui il parsing di dates con fast_strptime() specificando la stringa di formato appropriata.
Confronta i tempi di fast_strptime() con fasttime e ymd_hms().

Esercizio pratico interattivo

Prova a risolvere questo esercizio completando il codice di esempio.

# 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)

Modifica ed esegui il codice

Questo esercizio fa parte del corso

Lavorare con date e orari in R

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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: Fusi orari Exercise 2: Impostare il fuso orario Exercise 3: Visualizzare in un fuso orario Exercise 4: Fusi orari nei dati meteo Exercise 5: Orari senza date Exercise 6: Altre informazioni su importazione ed esportazione di date-ora Exercise 7: Parsing veloce con fasttime Exercise 8: Parsing veloce con lubridate::fast_strptime

Esercizio in corso

Exercise 9: Stampare date e orari in modo gradevole Exercise 10: Riepilogo