How to subtract add days from to a date

Question

I m trying to build folders to store data pulls  I want to label the folders with the day of that data in the pull   Ex  I pull 5 days ago data from mysql i want to name the folder the date from 5 days ago   MySQL can easily handle date arithmetic  I m not sure exactly how R does it  Should i just subtract the appropriate number of seconds in POSIXct and then convert to POSIXlt to name the folder MM DD YYYY   Or is there a better way

User · Answer

The answer probably depends on what format your date is in, but here is an example using the Date class:

dt <- as.Date("2010/02/10")
new.dt <- dt - as.difftime(2, unit="days")

You can even play with different units like weeks.

User · Answer

Just subtract a number    gt  as Date  2009-10-01    1   2009-10-01   gt  as Date  2009-10-01  -5  1   2009-09-26    Since the Date class only has days  you can just do basic arithmetic on it   If you want to use POSIXlt for some reason  then you can use it s slots    gt  a  lt - as POSIXlt  2009-10-04    gt  names unclass as POSIXlt  2009-10-04      1   sec     min     hour    mday    mon     year    wday    yday    isdst   gt  a mday  lt - a mday - 6  gt  a  1   2009-09-28 EDT

User · Answer

There is of course a lubridate solution for this   library lubridate  date  lt -  2009-10-01   ymd date  - 5    1   2009-09-26    is the same as  ymd date  - days 5     1   2009-09-26    Other time formats could be   ymd date  - months 5     1   2009-05-01   ymd date  - years 5     1   2004-10-01   ymd date  - years 1  - months 2  - days 3     1   2008-07-29

[r] How to subtract/add days from/to a date?

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