Sum aggregation in elastic search - r

Question

I have a data (df) in this format. I need to covert the Time stamp (tweetCreatedAt) into a date object so that I can further manipulate the data.
tweetCreatedAt comment_text
1 2014-05-17T00:00:49.000Z #truthout: India Elects Hard-Right Hindu
2 2014-05-17T00:00:49.000Z Narendra Modi is welcome to visit US !
Any help?
I have tried the following
df[,1] <- lapply(df[,1],function(x) as.POSIXct(x, '%Y-%m-%dT%H:%M:%S'))
But now I'm getting the dates only and not the actual time.

Answer 1

Not sure if this is the problem, but it's a possible one.
As I've mentioned in my comment, the elements of a column could be values, or lists, due to the process that generated this dataset.
Check this example:
# simplified example
dt = read.table(text = "tweetCreatedAt comment_text
1 2014-05-17T00:00:49.000Z #truthout
2 2014-05-19T00:00:49.000Z Narendra", header=T)
dt$tweetCreatedAt = as.character(dt$tweetCreatedAt)
# data set looks like
dt
# tweetCreatedAt comment_text
# 1 2014-05-17T00:00:49.000Z #truthout
# 2 2014-05-19T00:00:49.000Z Narendra
as.POSIXct(dt$tweetCreatedAt, format='%Y-%m-%dT%H:%M:%S')
# [1] "2014-05-17 00:00:49 BST" "2014-05-19 00:00:49 BST"
# let's manually change this element to a list
dt$tweetCreatedAt[2] = list(c("2014-05-19T00:00:49.000Z","2014-05-20T00:00:49.000Z"))
# data set now looks like this
dt
# tweetCreatedAt comment_text
# 1 2014-05-17T00:00:49.000Z #truthout
# 2 2014-05-19T00:00:49.000Z, 2014-05-20T00:00:49.000Z Narendra
as.POSIXct(dt$tweetCreatedAt, format='%Y-%m-%dT%H:%M:%S')
# Error in as.POSIXct.default(dt$tweetCreatedAt, format = "%Y-%m-%dT%H:%M:%S") :
# do not know how to convert 'dt$tweetCreatedAt' to class “POSIXct”