计算从特定日期到今天的天数r

Question

Data:

 DB <- data.frame(orderID  = c(1,2,3,4,5,6,7,8,9,10),     
   orderDate = c("1.1.14","16.3.14","11.5.14","21.6.14","29.7.14", 
        "2.8.14","21.9.14","4.10.14","30.11.14","2.1.15"),  
   itemID = c(2,3,2,5,12,4,2,3,1,5),  
   price = c(29.90, 39.90, 29.90, 19.90, 49.90, 9.90, 29.90, 39.90, 
              14.90, 19.90),
   customerID = c(1, 2, 3, 1, 1, 3, 2, 2, 1, 1),
   dateofbirth = c("12.1.67","14.10.82","6.8.87","12.1.67","12.1.67",
           "6.8.87","14.10.82","14.10.82","12.1.67","12.1.67")

Expected outcome [Hope I counted the number of days right]:

1.daystilllastorder(here 18.02.2015) = c("47", "137", "200", "47",
"47", "200", "137", "137", "47", "47")
2.daysbetweenthelastorders = c("33", "13","83","33", "33", "83", "13", "13", "33", "33",)

Hi guys,

unfortunately I have 3 new problems I´m not able to solve alone - so I would be very pleased if you peeps help me again :) In the data set every order got its own id and every registered user has his unique customerID. Every customer can order items (with ItemIDs), which got specific prices. User has his/her date of birth written in the data bank(as you can see above :D ) I want 1. Count the number of days from last order (of every customer) till today. 2. Count the number of days between the actual(newest) and the 2. newest order 3. Round the number of days between the orders in total

4. The number of orders during the last full year (Not from today(23.02.2015)-the full year:here 1.1.2014-31.12.2014) When system Date is switching to 2016, it should show me the number of orders in 2015 and so on:hope it´s understandable...

Tried it already like this, but it´s not working:

setDT(DB)[, orderDate := as.Date(orderDate, format = "%Y-%m-%d")] 
DB[, daystilllastorder := sum(seq[max(orderDate),Sys.Date(),  by = customerID]
DB$orderDate <- as.factor(DB$orderDate)     

Hope your able to show me what´s wrong or show me another posibility to solve the prob....

Cheers and THX!

Answer 1

Here's a possible solution (I don't know if I understood the 3 point correctly, but it seems like you want the average difference between orders?)

First we will convert orderDate to an actuall date class, then everything is straight forward

setDT(DB)[, orderDate := as.Date(orderDate, "%d.%m.%y")]

DB[,  `:=`(
           daystillastord = Sys.Date() - max(orderDate),
           daysbetlastord = if(.N == 1L) "first order" else as.character(max(orderDate) - max(orderDate[orderDate != max(orderDate)])),
           meandiff = mean(diff(orderDate)),
           OrdsLastFullYear = sum(year(orderDate) == year(Sys.Date()) - 1)
           ),
   by = customerID][]

#     orderID  orderDate itemID price customerID dateofbirth daystillastord daysbetlastord meandiff OrdsLastFullYear
#  1:       1 2014-01-01      2  29.9          1     12.1.67        52 days             33     91.5                4
#  2:       2 2014-03-16      3  39.9          2    14.10.82       142 days             13    101.0                3
#  3:       3 2014-05-11      2  29.9          3      6.8.87       205 days             83     83.0                2
#  4:       4 2014-06-21      5  19.9          1     12.1.67        52 days             33     91.5                4
#  5:       5 2014-07-29     12  49.9          1     12.1.67        52 days             33     91.5                4
#  6:       6 2014-08-02      4   9.9          3      6.8.87       205 days             83     83.0                2
#  7:       7 2014-09-21      2  29.9          2    14.10.82       142 days             13    101.0                3
#  8:       8 2014-10-04      3  39.9          2    14.10.82       142 days             13    101.0                3
#  9:       9 2014-11-30      1  14.9          1     12.1.67        52 days             33     91.5                4
# 10:      10 2015-01-02      5  19.9          1     12.1.67        52 days             33     91.5                4