How to Transform a Factor Variable into a Date

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How to Transform a Factor Variable into a Date

PaulJr
Dear all,

Hope you are doing great. I have a .csv file that I read into R, the .csv
file consistss of two fields (TransitDate and CargoTons).

The TransitDate I formatted from Excel in the fashion mmm-yy (e.g.:
Apr-2013). However R does not recognize the field TransitDate as a date
field.

Here is the code:

library(lubridate)

Dataset <- read.table("U:/NEWCargoData.csv", header=TRUE, sep=",",
na.strings="NA", dec=".", strip.white=TRUE)

DatasetFrame <- data.frame(Dataset)

DatasetFrame$TransitDate <- as.Date(DatasetFrame$TransitDate, format =
"%b-%y")


Now, when I do DatasetFrame[1,1], the following happens:


> DatasetFrame[1,1]
[1] NA
>
> DatasetFrame[2,1]
[1] NA
>

Now when I do:

> Dataset[1,1] #this is the dataset as was read from my computer
[1] Jun-11
62 Levels: Apr-13 Apr-14 Apr-15 Apr-16 Apr-17 Aug-13 Aug-14 Aug-15 Aug-16
Dec-12 Dec-13 Dec-14 ... Sep-16
>

I am also attaching the .csv file for your reference. How can I do to get R
to convert TransitDate into an actual date  field? R is not recognizing it
as a date.

Any help will be greatly appreciated,

Best regards,

Paul
______________________________________________
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Re: How to Transform a Factor Variable into a Date

Christopher W. Ryan
A couple thoughts:

1. converting factors into dates often requires that they be converted to
character first.

2. you don't really have dates; you have just months and years

3. therefore perhaps the as.yearmon() function in the zoo package could help

library(zoo)
my.factor <- factor("Feb 2017")
as.yearmon(my.factor)  ## gets around the factor-vs-character issue


On Mon, Jun 19, 2017 at 3:07 PM, Paul Bernal <[hidden email]> wrote:

> Dear all,
>
> Hope you are doing great. I have a .csv file that I read into R, the .csv
> file consistss of two fields (TransitDate and CargoTons).
>
> The TransitDate I formatted from Excel in the fashion mmm-yy (e.g.:
> Apr-2013). However R does not recognize the field TransitDate as a date
> field.
>
> Here is the code:
>
> library(lubridate)
>
> Dataset <- read.table("U:/NEWCargoData.csv", header=TRUE, sep=",",
> na.strings="NA", dec=".", strip.white=TRUE)
>
> DatasetFrame <- data.frame(Dataset)
>
> DatasetFrame$TransitDate <- as.Date(DatasetFrame$TransitDate, format =
> "%b-%y")
>
>
> Now, when I do DatasetFrame[1,1], the following happens:
>
>
> > DatasetFrame[1,1]
> [1] NA
> >
> > DatasetFrame[2,1]
> [1] NA
> >
>
> Now when I do:
>
> > Dataset[1,1] #this is the dataset as was read from my computer
> [1] Jun-11
> 62 Levels: Apr-13 Apr-14 Apr-15 Apr-16 Apr-17 Aug-13 Aug-14 Aug-15 Aug-16
> Dec-12 Dec-13 Dec-14 ... Sep-16
> >
>
> I am also attaching the .csv file for your reference. How can I do to get R
> to convert TransitDate into an actual date  field? R is not recognizing it
> as a date.
>
> Any help will be greatly appreciated,
>
> Best regards,
>
> Paul
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/
> posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

        [[alternative HTML version deleted]]

______________________________________________
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and provide commented, minimal, self-contained, reproducible code.
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Re: How to Transform a Factor Variable into a Date

Rui Barradas
Hello,

Another way of getting dates, of class 'Date', is to paste a day "01"
into what the op has.
To the op:
1) Your attachment didn't come through, R-Help doesn't accept the
extension .csv, use .txt
2) When you read your data in using function read.csv the result already
is a data.frame so the instruction

DatasetFrame <- data.frame(Dataset)

is not needed.
3) You can read the data and create a data.frame without the problem of
getting factors instead of characters, just set option

stringsAsFactors = FALSE

in your calls to read.*

And now some code. Note that I've made up some data, since we don't have
the .csv file.


x <- "Jun-11"
Dataset <- data.frame(x)
str(Dataset)

tmp <- paste("01", as.character(Dataset$x), sep = "-")
Dataset$x <- as.Date(tmp, format = "%d-%b-%y")
str(Dataset)


Hope this helps,

Rui Barradas

Em 19-06-2017 20:30, Christopher W Ryan escreveu:

> A couple thoughts:
>
> 1. converting factors into dates often requires that they be converted to
> character first.
>
> 2. you don't really have dates; you have just months and years
>
> 3. therefore perhaps the as.yearmon() function in the zoo package could help
>
> library(zoo)
> my.factor <- factor("Feb 2017")
> as.yearmon(my.factor)  ## gets around the factor-vs-character issue
>
>
> On Mon, Jun 19, 2017 at 3:07 PM, Paul Bernal <[hidden email]> wrote:
>
>> Dear all,
>>
>> Hope you are doing great. I have a .csv file that I read into R, the .csv
>> file consistss of two fields (TransitDate and CargoTons).
>>
>> The TransitDate I formatted from Excel in the fashion mmm-yy (e.g.:
>> Apr-2013). However R does not recognize the field TransitDate as a date
>> field.
>>
>> Here is the code:
>>
>> library(lubridate)
>>
>> Dataset <- read.table("U:/NEWCargoData.csv", header=TRUE, sep=",",
>> na.strings="NA", dec=".", strip.white=TRUE)
>>
>> DatasetFrame <- data.frame(Dataset)
>>
>> DatasetFrame$TransitDate <- as.Date(DatasetFrame$TransitDate, format =
>> "%b-%y")
>>
>>
>> Now, when I do DatasetFrame[1,1], the following happens:
>>
>>
>>> DatasetFrame[1,1]
>> [1] NA
>>>
>>> DatasetFrame[2,1]
>> [1] NA
>>>
>>
>> Now when I do:
>>
>>> Dataset[1,1] #this is the dataset as was read from my computer
>> [1] Jun-11
>> 62 Levels: Apr-13 Apr-14 Apr-15 Apr-16 Apr-17 Aug-13 Aug-14 Aug-15 Aug-16
>> Dec-12 Dec-13 Dec-14 ... Sep-16
>>>
>>
>> I am also attaching the .csv file for your reference. How can I do to get R
>> to convert TransitDate into an actual date  field? R is not recognizing it
>> as a date.
>>
>> Any help will be greatly appreciated,
>>
>> Best regards,
>>
>> Paul
>> ______________________________________________
>> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/
>> posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> [hidden email] mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
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Re: How to Transform a Factor Variable into a Date

David Carlson
In reply to this post by PaulJr
The R list does not recognize .csv files so your attachment got stripped. It is picky that way. Tacking .txt to the end might trick it into preserving the attachment.

Dataset <- read.table()

created a data.frame called Dataset so the second command was redundant. Probably better would be read.csv() which automatically uses "," as the separator. Also including the argument as.is=TRUE will prevent conversion of character fields to factors. Then your conversion to dates should work once you add a day to the month-year format (e.g. first of the month or middle of the month):

> Test <- read.csv(text='"TransitDate", "CargoTons"
+ "Apr-2013", 50
+ "Jun-2013", 40
+ "Jul-2013", 30', as.is=TRUE)
> Test$TransitDate <- as.Date(paste0("01-", Test$TransitDate), "%d-%b-%Y")
> str(Test)
'data.frame':   3 obs. of  2 variables:
 $ TransitDate: Date, format: "2013-04-01" "2013-06-01" ...
 $ CargoTons  : int  50 40 30
> Test
  TransitDate CargoTons
1  2013-04-01        50
2  2013-06-01        40
3  2013-07-01        30

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352



-----Original Message-----
From: R-help [mailto:[hidden email]] On Behalf Of Paul Bernal
Sent: Monday, June 19, 2017 2:07 PM
To: [hidden email]
Subject: [R] How to Transform a Factor Variable into a Date

Dear all,

Hope you are doing great. I have a .csv file that I read into R, the .csv
file consistss of two fields (TransitDate and CargoTons).

The TransitDate I formatted from Excel in the fashion mmm-yy (e.g.:
Apr-2013). However R does not recognize the field TransitDate as a date
field.

Here is the code:

library(lubridate)

Dataset <- read.table("U:/NEWCargoData.csv", header=TRUE, sep=",",
na.strings="NA", dec=".", strip.white=TRUE)

DatasetFrame <- data.frame(Dataset)

DatasetFrame$TransitDate <- as.Date(DatasetFrame$TransitDate, format =
"%b-%y")


Now, when I do DatasetFrame[1,1], the following happens:


> DatasetFrame[1,1]
[1] NA
>
> DatasetFrame[2,1]
[1] NA
>

Now when I do:

> Dataset[1,1] #this is the dataset as was read from my computer
[1] Jun-11
62 Levels: Apr-13 Apr-14 Apr-15 Apr-16 Apr-17 Aug-13 Aug-14 Aug-15 Aug-16
Dec-12 Dec-13 Dec-14 ... Sep-16
>

I am also attaching the .csv file for your reference. How can I do to get R
to convert TransitDate into an actual date  field? R is not recognizing it
as a date.

Any help will be greatly appreciated,

Best regards,

Paul
______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.