Skip to content

Reading and converting time data via read.table

5 messages · Ek Esawi, Jim Lemon, PIKAL Petr +2 more

Original
Ek Esawi
# 
Hi All--



I am relatively new to R. I am reading a csv file via read.table (MyFile).
The data types in the file are date, string, integer, and time. I was able
to read all the data and manipulated correctly except time, e.g., 12:30. I
used as.Date to convert date and string and integer were easily done. I
could not figure out how to convert the time data correctly. I tried chron
but w/o success and I read that POSIXlt and POSIXct work only for date and
time (e.g. 01/02/1999, 12:30:20). I did not try the lubridate package. Is
there a way to read time data without date attached to it like mine?



I am grateful for any help and thanks in advance?EKE



Here is an example of my data when read into R via read.table



                AA          Date         Name     T1          T2
N1

1              312171  7/1/1995       OF      13:37      1:43         123
Jim Lemon
# 
Hi EKE,
Your problem may be that the date strings are being read as a factor.
Try using stringsAsFactors=FALSE when you read the data in. Another
way is to convert your dates to strings when passing to as.Date:

as.Date(as.character(mydf$Date),"%m/%d/%Y")

Jim
On Sun, Jun 5, 2016 at 10:53 PM, Ek Esawi <esawiek at gmail.com> wrote:
PIKAL Petr
# 
Hi
If you used strptime for converting your datae/time value you can tune it by format to be able to read differently formated data.
[1] "1999-02-01 12:30:20 CET"
[1] "1999-02-01 12:30:00 CET"
[1] "1999-02-01 12:00:00 CET"
POSIXlt[1:1], format: "1999-02-01 12:00:00"
Regards
Petr
________________________________
Tento e-mail a jak?koliv k n?mu p?ipojen? dokumenty jsou d?v?rn? a jsou ur?eny pouze jeho adres?t?m.
Jestli?e jste obdr?el(a) tento e-mail omylem, informujte laskav? neprodlen? jeho odes?latele. Obsah tohoto emailu i s p??lohami a jeho kopie vyma?te ze sv?ho syst?mu.
Nejste-li zam??len?m adres?tem tohoto emailu, nejste opr?vn?ni tento email jakkoliv u??vat, roz?i?ovat, kop?rovat ?i zve?ej?ovat.
Odes?latel e-mailu neodpov?d? za eventu?ln? ?kodu zp?sobenou modifikacemi ?i zpo?d?n?m p?enosu e-mailu.

V p??pad?, ?e je tento e-mail sou??st? obchodn?ho jedn?n?:
- vyhrazuje si odes?latel pr?vo ukon?it kdykoliv jedn?n? o uzav?en? smlouvy, a to z jak?hokoliv d?vodu i bez uveden? d?vodu.
- a obsahuje-li nab?dku, je adres?t opr?vn?n nab?dku bezodkladn? p?ijmout; Odes?latel tohoto e-mailu (nab?dky) vylu?uje p?ijet? nab?dky ze strany p??jemce s dodatkem ?i odchylkou.
- trv? odes?latel na tom, ?e p??slu?n? smlouva je uzav?ena teprve v?slovn?m dosa?en?m shody na v?ech jej?ch n?le?itostech.
- odes?latel tohoto emailu informuje, ?e nen? opr?vn?n uzav?rat za spole?nost ??dn? smlouvy s v?jimkou p??pad?, kdy k tomu byl p?semn? zmocn?n nebo p?semn? pov??en a takov? pov??en? nebo pln? moc byly adres?tovi tohoto emailu p??padn? osob?, kterou adres?t zastupuje, p?edlo?eny nebo jejich existence je adres?tovi ?i osob? j?m zastoupen? zn?m?.

This e-mail and any documents attached to it may be confidential and are intended only for its intended recipients.
If you received this e-mail by mistake, please immediately inform its sender. Delete the contents of this e-mail with all attachments and its copies from your system.
If you are not the intended recipient of this e-mail, you are not authorized to use, disseminate, copy or disclose this e-mail in any manner.
The sender of this e-mail shall not be liable for any possible damage caused by modifications of the e-mail or by delay with transfer of the email.

In case that this e-mail forms part of business dealings:
- the sender reserves the right to end negotiations about entering into a contract in any time, for any reason, and without stating any reasoning.
- if the e-mail contains an offer, the recipient is entitled to immediately accept such offer; The sender of this e-mail (offer) excludes any acceptance of the offer on the part of the recipient containing any amendment or variation.
- the sender insists on that the respective contract is concluded only upon an express mutual agreement on all its aspects.
- the sender of this e-mail informs that he/she is not authorized to enter into any contracts on behalf of the company except for cases in which he/she is expressly authorized to do so in writing, and such authorization or power of attorney is submitted to the recipient or the person represented by the recipient, or the existence of such authorization is known to the recipient of the person represented by the recipient.
2 days later
MacQueen, Don
# 
As far as I know, base R does not have a class for storing times that are
not associated with a date, and recognizing that they are times. That
being the case, I don't think there is a way to convert them to some sort
of time class while reading them into R using read.table(). I would read
them into R as character strings, and then convert them (it would take
only a few extra lines of code). How you convert them depends on the next
question, which is:

What do you need to do with those times?

For example, are T1 and T2 the times associated with two events that both
occurred on the specified Date? If that is the case, I would probably form
two POSIXct variables by combining the Date with T1 and the Date with T2.
Or, do you just need to be able to sort your data by T1, or by T2? Or do
you need to calculate the time differences (such as T2-T1) to get the
number of minutes between those two times?

-Don
Jeff Newmiller
# 
The canonical way to store times is as difftime vectors.  However, there is no simple way to import e.g. HH:MM data directly into such vectors, so you need to embed such times into a longer string that includes a fixed date. After conversion to POSIXct you can subtract the fixed date to get the difftime values.

It is also possible to let the conversion to POSIXct pick "today" by default, but you can sometimes get into trouble if you subtract out "today" on a different day, so I wouldn't recommend it. 

You also may encounter difficulty with daylight savings in this process... but that usually requires knowing a bit more about your data, and if you are already working with time only data you may not be able to fix such problems anyway.