CODEWITHSUNDEEP
rdatetimeposixct
UDE_Student
UDE_Student

Reputation: 349

converting to posixct fails

> resulttable[3,1]
     UTC FORECAST TIME
1: 2018-05-01 00:30:00
> as.POSIXct(resulttable[3,1],format="%Y-%m-%d %H:%M:%S",tz="UTC")
Error in as.POSIXct.default(resulttable[3, 1], format = "%Y-%m-%d %H:%M:%S",  :       
do not know how to convert 'resulttable[3, 1]' to class “POSIXct”

I don't understand the error, because the first column of resulttable is formatted as posixct

> lapply(resulttable,class)
$`UTC FORECAST TIME`
[1] "POSIXct" "POSIXt" 

$`UTC FORECAST RECEIVE TIME`
[1] "POSIXct" "POSIXt"

Why does as.POSIXct(resulttable[3,1],format="%Y-%m-%d %H:%M:%S",tz="UTC") lead to an error?

edit: Here the output of str:

> str(resulttable[3,1])
Classes ‘data.table’ and 'data.frame':  1 obs. of  1 variable:
 $ UTC FORECAST TIME: POSIXct, format: "2018-05-01 00:30:00"
 - attr(*, ".internal.selfref")=<externalptr>

Upvotes: 1

Views: 1782

Answers (1)

Rui Barradas
Rui Barradas

Reputation: 76402

Note the output of str(resulttable[3,1]). It says that it is an object of classes data.table and data.frame. Therefore, you must extract the column or columns you want to convert to POSIXct with the standard extraction operators.

resulttable[3, 1][[1]]                   # a vector
resulttable[3, 1]$`UTC FORECAST TIME`    # the same vector

Note that the column name, UTC FORECAST TIME has spaces in it so you need to put it between back quotes.
Then, in order to do the conversion you can use any of the above forms.

as.POSIXct(resulttable[3,1][[1]], format = "%Y-%m-%d %H:%M:%S", tz = "UTC")
as.POSIXct(resulttable[3,1]$`UTC FORECAST TIME`, format = "%Y-%m-%d %H:%M:%S", tz = "UTC")

Upvotes: 2

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