Parse date-times from Elasticsearch records

Given a data.table with date-time strings, this function converts those dates-times to type POSIXct with the appropriate time zone. Assumption is that dates are of the form "2016-07-25T22:15:19Z" where T is just a separator and the last letter is a military timezone.

This is a side-effect-free function: it returns a new data.table and the input data.table is unmodified.

Usage

parse_date_time(input_df, date_cols, assume_tz = "UTC")

Arguments

input_df

a data.table with one or more date-time columns you want to convert

date_cols

Character vector of column names to convert. Columns should have string dates of the form "2016-07-25T22:15:19Z".

assume_tz

Timezone to convert to if parsing fails. Default is UTC

References

https://www.timeanddate.com/time/zones/military

https://en.wikipedia.org/wiki/List_of_tz_database_time_zones

Examples

# Sample es_search(), chomp_hits(), or chomp_aggs() output:
someDT <- data.table::data.table(id = 1:5
                                 , company = c("Apple", "Apple", "Banana", "Banana", "Cucumber")
                                 , timestamp = c("2015-03-14T09:26:53B", "2015-03-14T09:26:54B"
                                                 , "2031-06-28T08:53:07Z", "2031-06-28T08:53:08Z"
                                                 , "2000-01-01"))

# Note that the date field is character right now
str(someDT)
#> Classes ‘data.table’ and 'data.frame':	5 obs. of  3 variables:
#>  $ id       : int  1 2 3 4 5
#>  $ company  : chr  "Apple" "Apple" "Banana" "Banana" ...
#>  $ timestamp: chr  "2015-03-14T09:26:53B" "2015-03-14T09:26:54B" "2031-06-28T08:53:07Z" "2031-06-28T08:53:08Z" ...
#>  - attr(*, ".internal.selfref")=<externalptr> 

# Let's fix that!
someDT <- parse_date_time(input_df = someDT
                          , date_cols = "timestamp"
                          , assume_tz = "UTC")
str(someDT)
#> Classes ‘data.table’ and 'data.frame':	5 obs. of  3 variables:
#>  $ id       : int  1 2 3 4 5
#>  $ company  : chr  "Apple" "Apple" "Banana" "Banana" ...
#>  $ timestamp: POSIXct, format: "2015-03-14 07:26:53" "2015-03-14 07:26:54" ...
#>  - attr(*, ".internal.selfref")=<externalptr>