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  1. library(data.table)
  2. library(magrittr)
  3. # 讀資料
  4. tao_b <-
  5.   fread(
  6.     "
  7.     Area Project Type Date       Price
  8.     A    x       J    2012/6/18  1.1
  9.     A    x       J    2012/7/2   2.1
  10.     A    x       J    2012/7/6   3.2
  11.     A    x       J    2012/7/9   2.5
  12.     A    y       K    2012/7/15  10
  13.     A    y       K    2012/7/18  20
  14.     B    z       L    2012/7/20  111
  15.     B    z       L    2012/7/23  221
  16.     B    z       L    2012/7/23  222
  17.     B    z       L    2012/7/24  110"
  18.   )
  19.  
  20. # 一些必要清理
  21. tao_b %>%
  22.   .[, Date := as.POSIXct(Date)] %>%
  23.   .[, Price := as.double(Price)] %>%
  24.   .[, Price.med := median(Price), by = Area:Date] %>%
  25.   setorder(., Area, Project, Type, Date)
  26.  
  27. res <-
  28.   tao_b %>%
  29.   cbind(.,
  30.         Date.previous = tao_b[, c(Date[1], Date[1:(.N - 1)]), by = Area:Type]$V1,
  31.         Price.med.previous = tao_b[, c(NA, Price.med[1:(.N - 1)]), by = Area:Type]$V1) %>%
  32.   .[, c("delta.Price.med", "delta.Date") :=
  33.       list(ifelse(is.na(Price.med.previous), 0, Price.med - Price.med.previous),
  34.            ifelse(is.na(Date.previous), 0, (Date - Date.previous) / 60 / 60 / 24))]
  35.  
  36. tao_b
  37. res
  38.  
Success #stdin #stdout 0.29s 190080KB
comments (?)
stdin 
Standard input is empty
stdout 
    Area Project Type       Date Price Price.med
 1:    A       x    J 2012-06-18   1.1       1.1
 2:    A       x    J 2012-07-02   2.1       2.1
 3:    A       x    J 2012-07-06   3.2       3.2
 4:    A       x    J 2012-07-09   2.5       2.5
 5:    A       y    K 2012-07-15  10.0      10.0
 6:    A       y    K 2012-07-18  20.0      20.0
 7:    B       z    L 2012-07-20 111.0     111.0
 8:    B       z    L 2012-07-23 221.0     221.5
 9:    B       z    L 2012-07-23 222.0     221.5
10:    B       z    L 2012-07-24 110.0     110.0
    Area Project Type       Date Price Price.med Date.previous
 1:    A       x    J 2012-06-18   1.1       1.1    2012-06-18
 2:    A       x    J 2012-07-02   2.1       2.1    2012-06-18
 3:    A       x    J 2012-07-06   3.2       3.2    2012-07-02
 4:    A       x    J 2012-07-09   2.5       2.5    2012-07-06
 5:    A       y    K 2012-07-15  10.0      10.0    2012-07-15
 6:    A       y    K 2012-07-18  20.0      20.0    2012-07-15
 7:    B       z    L 2012-07-20 111.0     111.0    2012-07-20
 8:    B       z    L 2012-07-23 221.0     221.5    2012-07-20
 9:    B       z    L 2012-07-23 222.0     221.5    2012-07-23
10:    B       z    L 2012-07-24 110.0     110.0    2012-07-23
    Price.med.previous delta.Price.med delta.Date
 1:                 NA             0.0          0
 2:                1.1             1.0         14
 3:                2.1             1.1          4
 4:                3.2            -0.7          3
 5:                 NA             0.0          0
 6:               10.0            10.0          3
 7:                 NA             0.0          0
 8:              111.0           110.5          3
 9:              221.5             0.0          0
10:              221.5          -111.5          1
https://ideone.com/Aj4IX9
language:
R (R 3.5.2)
created:
5 years ago
visibility:
public

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