Sorting data frame based on month-year time format

Question

I\'m struggling with something very basic: sorting a data frame based on a time format (month-year, or, “%B-%y” in this case). My goal is to calculate various monthly statis

Answer 1

An old post but worthy of a data.table approach:

Read in data and set local as described by @caracal

> Sys.setlocale(category="LC_TIME", locale="Dutch_Belgium.1252")
[1] "Dutch_Belgium.1252"
> tmp09 <- read.table(file="clipboard", header=TRUE)
> tmp09$ExitTime <- as.Date(tmp09$ExitTime)

Summarise data as requested

require(data.table)
> data.table(tmp09)[, 
+                   .(Tmp09Total = sum(AccountValue)),
+                   by = .(Date = format(ExitTime, "%B-%y"))]
          Date Tmp09Total
1:    april-07       6997
2:      mei-07      21197
3:     juli-07      29147
4: augustus-07       7897
5: november-07       7423