TODO: unit tests for simil days
[talweg.git] / pkg / R / utils.R
1 #' dateIndexToInteger
2 #'
3 #' Transform a (potential) date index into an integer (relative to data beginning).
4 #'
5 #' @param index Date (or integer) index
6 #' @param data Object of class Data, output of \code{getData()}
7 #'
8 #' @export
9 dateIndexToInteger = function(index, data)
10 {
11 # Works on integers too: trust input
12 if (is.numeric(index))
13 index = as.integer(index)
14 if (is.integer(index))
15 return (index)
16
17 if (inherits(index, "Date") || is.character(index))
18 {
19 tryCatch(indexAsDate <- as.Date(index),
20 error=function(e) stop("Unrecognized index format"))
21 #TODO: tz arg to difftime ?
22 integerIndex <- round( as.numeric(
23 difftime(indexAsDate, as.Date(data$getTime(1)[1])) ) ) + 1
24 if (integerIndex >= 1 && integerIndex <= data$getSize())
25 return (integerIndex)
26 stop("Date outside data range")
27 }
28 stop("Unrecognized index format")
29 }
30
31 #' integerIndexToDate
32 #'
33 #' Transform an integer index (relative to data beginning) into a date index.
34 #'
35 #' @inheritParams dateIndexToInteger
36 #'
37 #' @export
38 integerIndexToDate = function(index, data)
39 {
40 # Works on dates too: trust input
41 if (is.character(index))
42 index = as.Date(index)
43 if (is(index,"Date"))
44 return (index)
45
46 index = index[1]
47 if (is.numeric(index))
48 index = as.integer(index)
49 if (!is.integer(index))
50 stop("'index' should be a date or integer")
51 as.Date( data$getTime(index)[1] )
52 }
53
54 #' getSimilarDaysIndices
55 #'
56 #' Find similar days indices in the past; at least same type of day in the week:
57 #' monday=tuesday=wednesday=thursday != friday != saturday != sunday.
58 #'
59 #' @param index Day index (numeric or date)
60 #' @param data Reference dataset, object output of \code{getData}
61 #' @param limit Maximum number of indices to return
62 #' @param same_season Should the indices correspond to day in same season?
63 #' @param days_in Optional set to intersect with results (NULL to discard)
64 #'
65 #' @export
66 getSimilarDaysIndices = function(index, data, limit, same_season, days_in=NULL)
67 {
68 index = dateIndexToInteger(index, data)
69
70 # Look for similar days (optionally in same season)
71 i = index - 1
72 days = c()
73 dt_ref = as.POSIXlt(data$getTime(index)[1]) #first date-time of current day
74 day_ref = dt_ref$wday #1=monday, ..., 6=saturday, 0=sunday
75 month_ref = as.POSIXlt(data$getTime(index)[1])$mon+1 #month in 1...12
76 while (i >= 1 && length(days) < limit)
77 {
78 dt = as.POSIXlt(data$getTime(i)[1])
79 if ((is.null(days_in) || i %in% days_in) && .isSameDay(dt$wday, day_ref))
80 {
81 if (!same_season || .isSameSeason(dt$mon+1, month_ref))
82 days = c(days, i)
83 }
84 i = i - 1
85 }
86 return ( days )
87 }
88
89 # isSameSeason
90 #
91 # Check if two months fall in the same "season" (defined by estimated pollution rate).
92 #
93 # @param month Month index to test
94 # @param month_ref Month to compare to
95 #
96 .isSameSeason = function(month, month_ref)
97 {
98 if (month_ref %in% c(11,12,1,2)) #~= mid-polluted
99 return (month %in% c(11,12,1,2))
100 if (month_ref %in% c(3,4,9,10)) #~= high-polluted
101 return (month %in% c(3,4,9,10))
102 return (month %in% c(5,6,7,8)) #~= non polluted
103 }
104
105 # isSameDay
106 #
107 # Monday=Tuesday=Wednesday=Thursday ; Friday, Saturday, Sunday: specials.
108 #
109 # @param day Day index to test
110 # @param day_ref Day index to compare to
111 #
112 .isSameDay = function(day, day_ref)
113 {
114 if (day_ref == 0)
115 return (day==0)
116 if (day_ref <= 4)
117 return (day <= 4)
118 return (day == day_ref)
119 }