Re: [R] unable to subtract dates in R

Rui Barradas Wed, 11 Jul 2012 16:31:14 -0700

Hello,

1. Post a data example,


dput(head(intakeDS, 20)) # post the output of this

2. You are subtracting IntakeDate from DOB, when it should be the otherway around. Like this you get negative dates and those are illegal.


If this point 2 doesn't solve it, follow step 1.

Hope this helps,

Rui Barradas

Em 11-07-2012 23:20, William Mabe escreveu:

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

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