[R] unable to subtract dates in R

[arun]

Hi William,
Glad to know that.

So, I guess "difftime()" did the trick if both befong to the class "Date".

A.K.





________________________________
From: William Mabe <billmabe at gmail.com>
To: arun <smartpink111 at yahoo.com> 
Sent: Thursday, July 12, 2012 1:12 PM
Subject: Re: [R] unable to subtract dates in R


Thanks Arun! That worked.


On Wed, Jul 11, 2012 at 8:17 PM, arun <smartpink111 at yahoo.com> wrote:

Hi,
>
>It is a bit difficult to give suggestions when there are no example datasets.
>Have you checked whether both belong to "Date" class?
>
>You could use,
>difftime(intakeDS$DOB, intakeDS$IntakeDate_d,units="days")
>to get the difference between dates
>A.K.
>
>
>
>
>
>----- Original Message -----
>From: William Mabe <billmabe at gmail.com>
>To: r-help at r-project.org
>Cc:
>Sent: Wednesday, July 11, 2012 6:20 PM
>Subject: [R] unable to subtract dates in R
>
>Hi,
>
>I wanted to calculate the age of people in my dataset by subtracting the
>individual's date of birth from their intake into a program.
>
>After several hours, searches of help archives, and the downloading of
>lubiridate, I have had no luck with this.
>
>Below is the code I used.
>
>> intakeDS$DOB <- as.character(intakeDS$DOB)
>
>> intakeDS$DOB <- as.Date(intakeDS$DOB, "%Y%m%d")
>
>>
>
>> # Make IntakeDate a date variable, by first converting it from numeric to
>character then from character to date
>
>> #intakeDS$IntakeDate <- as.character(intakeDS$IntakeDate)
>
>> intakeDS$IntakeDate_d <- as.Date(intakeDS$IntakeDate_c, "%Y%m%d")
>
>>
>
>> intakeDS$intake_age <- intakeDS$DOB - intakeDS$IntakeDate_d
>
>> intakeDS$intake_age
>
>Time differences in days
>
>  [1] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA
>
>[61] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA
>
>[121] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA
>
>[181] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
>NA NA NA NA NA NA NA NA NA NA NA NA
>
>[241] NA NA NA NA NA NA NA
>
>
>I also downloaded the lubridate package and used the new_interval command
>and that created a variable that showed the start date and the end date.
>However, I was not able to subtract one date from the other to calculate an
>age variable.
>
>
>Any help would be greatly appreciated as this has been a pretty miserable
>afternoon hacking away at this.
>
>
>Thanks,
>
>Bill
>
>
>    [[alternative HTML version deleted]]
>
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>
>