14

This is the information contained within my dataframe:

## minuteofday: factor w/ 89501 levels "2013-06-01 08:07:00",...
## dDdt: num 7.8564 2.318 ...
## minutes: POSIXlt, format: NA NA NA

I need to convert the minute of day column to a date/time format:

minuteave$minutes <- as.POSIXlt(as.character(minuteave$minuteofday), format="%m/%d/%Y %H:%M:%S")

I've tried as.POSIXlt, as.POSIXct and as.Date. None of which worked. Does anyone have ANY thoughts.

The goal is to plot minutes vs. dDdt, but it won't let me plot in the specified time period that I want to as a factor. I have no idea what to try next...

Matthew Lundberg
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Michelle
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2 Answers2

25

You need to insert an as.character() before parsing as a Datetime or Date.

A factor will always come back first as a number corresponding to its level.

You can save the conversion from factor to character by telling read.csv() etc to no store as a factor: stringsAsFactors=FALSE. You can also set that as a global option.

Once you have it as character, make sure you match the format string to your data:

R> as.POSIXct("2013-06-01 08:07:00", format="%Y-%m-%d %H:%M:%S")
[1] "2013-06-01 08:07:00 CDT"
R>

Note the %Y-%m-%d I used, as opposed to your %m/%d/%y.

Edit on 3 Jan 2016: This is now much easier thanks to the anytime package which automagically converts from many types, including factor, and does so without requiring a format string.

R> as.factor("2013-06-01 08:07:00")
[1] 2013-06-01 08:07:00
Levels: 2013-06-01 08:07:00
R> 
R> library(anytime)
R> anytime(as.factor("2013-06-01 08:07:00"))
[1] "2013-06-01 08:07:00 CDT"
R> 
R> class(anytime(as.factor("2013-06-01 08:07:00")))
[1] "POSIXct" "POSIXt" 
R>

As you can see we just feed the factor variable into anytime() and out comes the desired POSIXct type.

Dirk Eddelbuettel
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  • I think he already inserted the `as.character` the problem is that he has an error in the format imo – David Arenburg Apr 28 '14 at 19:03
  • Thanks, I noticed that too on second read and expanded my answer. The remaining problem (which your answer repeats) is the `as.POSIXlt` conversion (without extracting minutes). – Dirk Eddelbuettel Apr 28 '14 at 19:05
9

Try this

library(lubridate)
minuteave$minutes <- ymd_hms(minuteave$minutes)

this will return minuteave$minutes as a POSIXct object.

Hope this helps you.

UseR10085
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darkage
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