CODEWITHSUNDEEP
rdatedifference
mrpargeter
mrpargeter

Reputation: 329

Calculate days between sequential dates in single column

I have the following dataframe containing a column of dates and a column of assessments: 

dates<-c("2015-01-02","2015-01-10","2016-01-15")
assessments<-c('1','2','3')
dates_dataframe = data.frame(dates, assessments)
dates_dataframe$dates<-as.Date(dates_dataframe$dates)

I want to create another column in this dataframe that contains the number of days between one assessment and the next.

How would I go about doing this?

Upvotes: 1

Views: 121

Answers (3)

acylam
acylam

Reputation: 18691

You can do this with diff:

dates_dataframe$days = c(0, diff(dates_dataframe$dates))
dates_dataframe$days2 = c(diff(dates_dataframe$dates), 0)

or with NAs:

dates_dataframe$days3 = c(NA, diff(dates_dataframe$dates))
dates_dataframe$days4 = c(diff(dates_dataframe$dates), NA_character_)

Result:

> dates_dataframe
       dates assessments days    days2 days3    days4
1 2015-01-02           1    0   8 days    NA   8 days
2 2015-01-10           2    8 370 days     8 370 days
3 2016-01-15           3  370   0 days   370  NA days

Upvotes: 2

Adam Warner
Adam Warner

Reputation: 1354

I think you should go with useR's answer but here is another one: 

dates<-c("2015-01-02","2015-01-10","2016-01-15")
assessments<-c('1','2','3')
dates_dataframe <- cbind.data.frame(dates, assessments)
dates_dataframe$dates <- as.Date(dates_dataframe$dates)
dates_dataframe$dates_shift = shift(dates_dataframe$dates,1)
dates_dataframe$days <- (dates_dataframe$dates - dates_dataframe$dates_shift)


   dates       assessments dates_shift  days
1 2015-01-02           1        <NA>  NA days
2 2015-01-10           2  2015-01-02   8 days
3 2016-01-15           3  2015-01-10 370 days

Upvotes: 1

YOLO
YOLO

Reputation: 21749

Another way is using shift function:

# create data
dates<-c("2015-01-02","2015-01-10","2016-01-15")
assessments<-c('1','2','3')
df <- data.table(dates, assessments)

# convert to date format
df[, dates := as.Date(dates)]

# shift
df[, next_dates := shift(dates, 1)]

# get difference
df[, difference := abs(next_dates - dates)]

        dates assessments next_dates difference
1: 2015-01-02           1       <NA>    NA days
2: 2015-01-10           2 2015-01-02     8 days
3: 2016-01-15           3 2015-01-10   370 days

Upvotes: 2

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