Aggregate daily level data to weekly level in R

Question

I have a huge dataset similar to the following reproducible sample data.

   Interval    value
1  2012-06-10   552
2  2012-06-11  4850
3  2012-06-12  4642
4          


        

Answer 1

I just came across this old question because it was used as a dupe target.

Unfortunately, all the upvoted answers (except the one by konvas and a now deleted one) present solutions for aggregating the data by week of the year while the OP has requested to aggregate by week of the month.

The definition of week of the year and week of the month is ambiguous as discussed here, here, and here.

However, the OP has indicated that he wants to count the days 1 to 7 of each month as week 1 of the month, days 8 to 14 as week 2 of the month, etc. Note that week 5 is a stub for most of the months consisting of only 2 or 3 days (except for the month of February if no leap year).

Having prepared the ground, here is a data.table solution for this kind of aggregation:

library(data.table)
DT[, .(value = sum(value)), 
       by = .(Interval = sprintf("Week %i, %s", 
                                 (mday(Interval) - 1L) %/% 7L + 1L, 
                                 format(Interval, "%b %Y")))]

           Interval value
1: Week 2, Jun 2012 18366
2: Week 3, Jun 2012 24104
3: Week 4, Jun 2012 23348
4: Week 5, Jun 2012  5204
5: Week 1, Jul 2012 23579
6: Week 2, Jul 2012 11573

We can verify that we have picked the correct intervals by

DT[, .(value = sum(value),
       date_range = toString(range(Interval))), 
   by = .(Week = sprintf("Week %i, %s", 
                             (mday(Interval) -1L) %/% 7L + 1L, 
                             format(Interval, "%b %Y")))]

               Week value             date_range
1: Week 2, Jun 2012 18366 2012-06-10, 2012-06-14
2: Week 3, Jun 2012 24104 2012-06-15, 2012-06-21
3: Week 4, Jun 2012 23348 2012-06-22, 2012-06-28
4: Week 5, Jun 2012  5204 2012-06-29, 2012-06-30
5: Week 1, Jul 2012 23579 2012-07-01, 2012-07-07
6: Week 2, Jul 2012 11573 2012-07-08, 2012-07-10

which is in line with OP's specification.

Data

library(data.table)
DT <- fread(
  "rn   Interval    value
  1  2012-06-10   552
  2  2012-06-11  4850
  3  2012-06-12  4642
  4  2012-06-13  4132
  5  2012-06-14  4190
  6  2012-06-15  4186
  7  2012-06-16  1139
  8  2012-06-17   490
  9  2012-06-18  5156
  10 2012-06-19  4430
  11 2012-06-20  4447
  12 2012-06-21  4256
  13 2012-06-22  3856
  14 2012-06-23  1163
  15 2012-06-24   564
  16 2012-06-25  4866
  17 2012-06-26  4421
  18 2012-06-27  4206
  19 2012-06-28  4272
  20 2012-06-29  3993
  21 2012-06-30  1211
  22 2012-07-01   698
  23 2012-07-02  5770
  24 2012-07-03  5103
  25 2012-07-04   775
  26 2012-07-05  5140
  27 2012-07-06  4868
  28 2012-07-07  1225
  29 2012-07-08   671
  30 2012-07-09  5726
  31 2012-07-10  5176", drop = 1L)
DT[, Interval := as.Date(Interval)]