Calculate number of days between two dates in r

Question

I need to calculate the number of days elapsed between multiple dates in two ways and then output those results to new columns: i) number of days that has elapsed as compare

Answer 1

This will get you what you want:

d <- as.Date(DATA$DATE, format="%m/%d/%Y")

first <- c()
for (i in seq_along(d))
    first[i] <- d[i] - d[1]

between <- c(0, diff(d))

This uses the as.Date() function in the base package to cast the vector of string dates to date values using the given format. Since you have dates as month/day/year, you specify format="%m/%d/%Y" to make sure it's interpreted correctly.

diff() is the lagged difference. Since it's lagged, it doesn't include the difference between element 1 and itself, so you can concatenate a 0.

Differences between Date objects are given in days by default.

Then constructing the output dataframe is simple:

RESULTS <- data.frame(DATE=DATA$DATE, FIRST=first, BETWEEN=between)