[R] Change data frame to time series data

[Enrico Schumann]

On Wed, 02 Oct 2024, roslinazairimah zakaria writes:

> Dear all, I have a data in data frame and would like to change to time
> series data. Thank you for any help given.
>
>> str(dt)'data.frame':	525600 obs. of  3 variables:
>  $ time             : chr  "2014-01-01 00:00:00" "2014-01-01 00:01:00"
> "2014-01-01 00:02:00" "2014-01-01 00:03:00" ...
>  $ cnt_charge_events: int  0 0 0 0 0 0 0 0 0 0 ...
>  $ count            : int  0 0 0 0 0 0 0 0 0 0 ...
>
>> head(dt)                 time cnt_charge_events count
> 1 2014-01-01 00:00:00                 0     0
> 2 2014-01-01 00:01:00                 0     0
> 3 2014-01-01 00:02:00                 0     0
> 4 2014-01-01 00:03:00                 0     0
> 5 2014-01-01 00:04:00                 0     0
> 6 2014-01-01 00:05:00                 0     0
>
>
>> dt_ts <- xts(dt$count, dt$time)Error in xts(dt$count, dt$time) :
>   order.by requires an appropriate time-based object> head(dt_ts)Time Series:
> Start = 1
> End = 6
> Frequency = 1
>   dt_ts.date dt_ts.time dt[, 3]
> 1      16071          1       0
> 2      16071          2       0
> 3      16071          3       0
> 4      16071          4       0
> 5      16071          5       0
> 6      16071          6       0Dear


Your "time" column consists of character strings, not
actual timestamps. 

  dt <- read.table(
  text ="
  time, cnt_charge_events, count
  2014-01-01 00:00:00, 1, 1 
  2014-01-01 00:01:00, 2, 2 
  2014-01-01 00:02:00, 3, 3 
  2014-01-01 00:03:00, 4, 4
  2014-01-01 00:04:00, 5, 5
  2014-01-01 00:05:00, 6, 6",
  header = TRUE, sep = ",")
  
  library("xts")
  xts(dt$count, dt$time)  ## won't work
  ## Error in xts(dt$count, dt$time) : 
  ##   order.by requires an appropriate time-based object
  
  dt$time <- as.POSIXct(dt$time)
  xts(dt$count, dt$time)
  ##                     [,1]
  ## 2014-01-01 00:00:00    1
  ## 2014-01-01 00:01:00    2
  ## 2014-01-01 00:02:00    3

But be sure to read about ?as.POSIXct; in particular,
the handling of timezones/daylight-saving time.


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-- 
Enrico Schumann
Lucerne, Switzerland
https://enricoschumann.net