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rdatedatetimedata.table
user45415631
user45415631

Reputation: 175

Operations with Dates (Subtract)

I have a column with dates:

  Time
1/1/2005
2/1/2005
3/1/2005
4/1/2005

How can I subtract one month from each date?

Upvotes: 0

Views: 1615

Answers (1)

Rich Scriven
Rich Scriven

Reputation: 99371

You can convert it to POSIXlt and subtract one from the mon attribute

(x <- as.POSIXlt(as.Date(df$Time, format = "%m/%d/%Y")))
# [1] "2005-01-01 UTC" "2005-02-01 UTC" "2005-03-01 UTC" "2005-04-01 UTC"
x$mon <- x$mon - 1
x
# [1] "2004-12-01 UTC" "2005-01-01 UTC" "2005-02-01 UTC" "2005-03-01 UTC"

Another option is to use lubridate

date <- as.Date(df$Time, format = "%m/%d/%Y")
library(lubridate)
month(date) <- month(date) - 1
date
# [1] "2004-12-01" "2005-01-01" "2005-02-01" "2005-03-01"

where df is

structure(list(Time = c("1/1/2005", "2/1/2005", "3/1/2005", "4/1/2005"
)), .Names = "Time", class = "data.frame", row.names = c(NA, 
-4L))

Upvotes: 1

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