Question on creating Date variable

# can use sprintf to convert to a number with 2 digit fractions
x <- c(10.30, 11, 11.01, 11.09, 11.15, 11.59, 12, 13)
as.POSIXct(sprintf("%.2f", x), format = "%H.%M")

HI,

Just by taking David's solution:
 y <- as.POSIXct(paste( floor(x), round(60*(x-floor(x))) ), format="%H %M")
 y1<-data.frame(y,AM_PM=format(y,format="%p"))
 y1[3,1]-y1[4,1]
#Time difference of -40 mins
 y1[5,1]-y1[3,1]
#Time difference of -13 mins
 head(y1,2)
#                    y AM_PM
#1 2013-01-01 11:00:00    AM
#2 2013-01-01 11:15:00    AM
A.K.





----- Original Message -----
From: Christofer Bogaso <bogaso.christofer at gmail.com>
To: David Winsemius <dwinsemius at comcast.net>; David L Carlson <dcarlson at tamu.edu>
Cc: r-help at r-project.org
Sent: Tuesday, January 1, 2013 12:40 AM
Subject: Re: [R] Question on creating Date variable

On 01 January 2013 03:00:18, David Winsemius wrote:

On Dec 31, 2012, at 11:57 AM, David Winsemius wrote:

On Dec 31, 2012, at 11:54 AM, Christofer Bogaso wrote:

On 01 January 2013 01:29:53, David Winsemius wrote:

On Dec 31, 2012, at 11:35 AM, Christofer Bogaso wrote:

On 01 January 2013 00:17:50, David Winsemius wrote:

On Dec 31, 2012, at 9:12 AM, Christofer Bogaso wrote:

Hello all,

Let say I have following (numeric) vector:

x

[1] 11.00 11.25 11.35 12.01 11.14 13.00 13.25 13.35 14.01 13.14
14.50
14.75 14.85 15.51 14.64

Now, I want to create a 'Date' variable (i.e. I should be able
to do
all calculations pertaining to date/time and also time-series
plotting etc.) like

2012-12-31 11:00:00 AM, 2012-12-31 11:25:00 AM, 2012-12-31 11:35:00
AM, 2012-12-31 12:01:00 PM, . . . .

Those _times_ ( _not_ Dates) cannot possibly be in %M.%S" format,
given the number of items to the right of the decimal point that are
greater than 60. So will proceed on the arguably more likely
assumption that they are in fractional minutes. To recover from that
problem, one might consider:

as.POSIXct(paste( floor(x), round(60*(x-floor(x))) ),

format="%M %S")
[1] "2012-12-31 00:11:00 PST" "2012-12-31 00:11:15 PST"
[3] "2012-12-31 00:11:21 PST" "2012-12-31 00:12:01 PST"
[5] "2012-12-31 00:11:08 PST" "2012-12-31 00:13:00 PST"
[7] "2012-12-31 00:13:15 PST" "2012-12-31 00:13:21 PST"
[9] "2012-12-31 00:14:01 PST" "2012-12-31 00:13:08 PST"
[11] "2012-12-31 00:14:30 PST" "2012-12-31 00:14:45 PST"
[13] "2012-12-31 00:14:51 PST" "2012-12-31 00:15:31 PST"
[15] "2012-12-31 00:14:38 PST"

I understand that some of those elements are not "dates". However
what I want is the ***"PM/AM" suffix*** on those elements which are
considered as Dates.

***Getting those suffix*** and doing calculations on those changed
variables is my primary concern.

That's the first time that AM/PM has bee mentioned and I suppose if
those were fractional hours rather than my guess of fractional minutes
that there might be representatives of both in the numeric data you
offered. Why don't you clarify what these number do in fact represent?
And what problem you are trying to solve?

Basically those are artificial data! Actually I do not have the
right to give out the original data in any public forum. So I
created those artificial data so that I can get the fundamental idea
...........

Each element (assuming they are legitimate time) represents the time
for a particular day when some event is pop-up. like, 11AM, 11.30AM,
12.05PM etc.. I could work with something like 11.00, 11.30, 12.05,
15.00 etc. however I believe adding AM/PM suffice will make my
report more eye-catching.

Please let me know if you need more clarification.

So what's with the values above 59 in the minutes?

Failing an answer to that question, this code shows how to input
date-time vectors from character vectors and then output it from
date-time class to character class:

 x <- scan(text="11.00 11.25 11.35 12.01 11.14 13.00 13.25 13.35 14.01
13.14 14.50 14.75 14.85 15.51 14.64")  # This will come in as a
numeric vector

?strptime     # for the available format specifications
format( as.POSIXct(as.character(x), format="%H.%M"),  # That is the
input format
             format="%I.%M %p")     # the output format
 [1] NA         "11.25 AM" "11.35 AM" "12.01 PM" "11.14 AM" NA
 [7] "01.25 PM" "01.35 PM" "02.01 PM" "01.14 PM" "02.05 PM" NA
[13] NA         "03.51 PM" NA

I suspect that the NA when minutes are ".00" comes from the implicit
loss of the trailing digits:

as.character(0.00)

[1] "0"

The claim that this data is proprietary and cannot presented in its
original form sound somewhat ridiculous.  Simmply post:

 dput(head(dfrm$time_data_column_name, 20))

How could that represent any disclosure of proprietary information if
presented with no context?

'How could that represent any disclosure of proprietary information if
presented with no context? ' I must agree with you. But I just dont
want to take any risk! (job scenario in my country is not very
optimistic and I want to give my boss minimal chance/reason to fire!)

And secondly with your approach, I cant do any calculation. Let take
following example:

y <- format( as.POSIXct(as.character(x), format="%H.%M"),  # That is
the input format
             format="%I.%M %p")

y[3] - y[2]

This gives me following error:

Error in y[3] - y[2] : non-numeric argument to binary operator

I am having same error with Devid's approach as well:

y <- as.POSIXct(paste( floor(x), round(60*(x-floor(x))) ), format="%H %M")
z <- format(y, format="%Y-%m-%d %I:%M %p")
z[2] - z[1]

Error in z[2] - z[1] : non-numeric argument to binary operator.

Thanks and regards,