Dates and Date-Times Classes

Barcelona R users Group

• Motivació
• Diferenciar entre Date i Date-time
• Converir Dates i Date-times
• Operacions amb Dates
• Package lubridate
• Sctipt exemple en R

Per les seves particularitats, les dates són complicades en general:

• Diferents formats (5/11/13, 11-05-2013, …)
• Hores, minuts, etc (2014-01-17 o 2014-01-17 14:14:32 CET)
• Diferents timezones (CET, CEST, …)
• Diferents locals

A l'R hi ha diferents classes que ho implementen, Date, POSIXct, chron, date.

• Date: Represents calendar dates in R.

Sys.Date()

[1] "2014-02-06"

• POSIXCT: Represents calendar dates and times in R.

Sys.time()

[1] "2014-02-06 19:14:12 CET"

Date

Number of days since 1970-01-01

POSIXct

Number of seconds since the beginning of 1970

POSIXlt

Named list of vectors sec, min , hour, etc

Character a Date

• as.Date (especificar format, accepta moltes classes)
• strftime
• ISOdate (character any, mes, dia per separat)

Date a Character

• as.character
• format

Garantia Hadley Wickham

“Dates and Times Mades Easy with lubridate package”

És útil per les següents tasques:

• Reconeixer formats de forma fàcil*
• Extreure components d'una Date-time*
• Calculs i operacions amb temps
• Tractar time zones

• Dates and Times Mades Easy with lubridate package
• Date-Time Classes (Rnews 2001)
• Date-Time Classes (Rnews 2004)
• Date time cheat sheet (lubridate)

• RStudio i RStudio R Presentations.
• Script, dades i codi presentació a github.

sessionInfo()

R version 3.0.2 (2013-09-25)
Platform: x86_64-apple-darwin10.8.0 (64-bit)

locale:
[1] es_ES.UTF-8/es_ES.UTF-8/es_ES.UTF-8/C/es_ES.UTF-8/es_ES.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] knitr_1.5

loaded via a namespace (and not attached):
[1] evaluate_0.5.1 formatR_0.10   stringr_0.6.2  tools_3.0.2