You don't need to do these operations in pieces so the mapply is unnecessary.
Neither dplyr nor data.table can go faster than (assuming your data frame is
called DF):
DF$dtm <- as.POSIXct( as.numeric( DF$ts ), tz="GMT", origin="1970-01-01" )
They can in this case save you from having to retype DF more than once, but in
this case even achieving that requires more typing than the above does.
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Sent from my phone. Please excuse my brevity.
On February 12, 2015 6:15:35 AM EST, arnaud gaboury <arnaud.gabo...@gmail.com>
wrote:
>I am little lost between all the possibilities to apply a function to
>a data.frame or data.table.
>
>Here is mine:
>
>structure(list(name = c("poisonivy", "poisonivy", "poisonivy",
>"poisonivy", "poisonivy", "poisonivy", "poisonivy", "poisonivy",
>"cruzecontrol", "agreenmamba", "agreenmamba", "vairis", "vairis",
>"vairis", "vairis", "vairis", "vairis", "xaeth"), text = c("ok",
>"need items ?", "i didn't submit pass codes for a long now",
>"ok", "<@U03AEKYL4>: what app are you talking about ?", "some testing
>with my irc client",
>"ha ha sorry", "for me there is no such question", "Lol.",
>"<@U03AEKWTL|agreenmamba> uploaded a file:
><https://enlightened.slack.com/files/agreenmamba/F03KGRF3W/screenshot_2015-02-09-14-31-15.png|regarding:
>should I stay or should I go?>",
>"<@U032FHV3S> <http://youtu.be/oGIFublvDes>", "ok, see you around",
>"yeah, I had a procrastination rush so I started to decode a little",
>"<http://ingress.com/intel|ingress.com/intel> when you submit
>passcodes",
>"intel", "what is the cooldown time or how does it work...;",
>"anybody knows how does \"Passcode circuitry too hot. Wait for cool
>down to enter another passcode.\" works?",
>"and people told that agent their geocities experience would never
>amount to anything (the convo yesterday) "
>), ts = c("1423594336.000138", "1423594311.000136",
>"1423594294.000135",
>"1423594258.000133", "1423594244.000131", "1423497058.000127",
>"1423497041.000126", "1423478555.000123", "1423494427.000125",
>"1423492370.000124", "1423478364.000121", "1423594358.000139",
>"1423594329.000137", "1423594264.000134", "1423594251.000132",
>"1423592204.000130", "1423592174.000129", "1423150354.000112"
>)), .Names = c("name", "text", "ts"), class = c("data.table",
>"data.frame"), row.names = c(NA, -18L))
>
>As you can see, it is of class data.frame and data.table.
>
>I need to work on last column "t"s. These are characters and are times
>in epoch format. I want to have time in Posix. I must thus do two
>things:
>- characters to numeric : myData$ts <- as.numeric(myData$ts)
>- epoch to Posix : mapply(as.POSIXct, tz = 'GMT', origin =
>'1970-01-01', myMerge$ts)
>
>I wonder:
>- if I can apply these two functions at the same time
>- what will be the fastest way : use dplyr package, or work with
>data.table ? My real data will be much more important than the one
>posted.
>
>Thank you for advice and hint.
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