Selecting a time period with window in R; format "dd/mm/yyyy h:m:s" (Windows 7)

Question

I have the following problem. I wanted to use the following code to select a specific time period for daily data, for instance this one:

window(Modellwind.zoo, start = as.Date("01/Jan/2001 12:00:00"), end = as.Date("4/Jan/2001 12:00:00"))

I get the following error message: Error in charToDate(x) : character string is not in a standard unambiguous format

When I tried to find an acceptable time format with the function anydate, it didnt work either:

library(anytime)
anydate("01/Jan/2001 12:00:00")

Using the following code:

window(Modellwind.zoo, start = as.Date("2001-01-01"), end = as.Date("2001-01-04"))

Unfortunately, I'm getting the following error:

 **Warning messages:
  1: In which(in.index & all.indexes >= start & all.indexes <= end) :
  Incompatible methods ("Ops.dates", "Ops.Date") for ">="
  2: In which(in.index & all.indexes >= start & all.indexes <= end) :
  Incompatible methods ("Ops.dates", "Ops.Date") for "<="**

The following code includes a sample of Modellwind.zoo.

structure(c(9.08093655399134, 6.51590181162631, 7.14637946155745, 
1.43900253813098, 6.78880326680026, 14.3182887821646, 16.3360242476697, 
16.1781018622214, 17.2200845065928, 15.6439142273171, 8.10504553259712, 
3.78898221928137, 6.78608582121557, 7.18116948778303, 5.0299974451978, 
3.49148782050232, 6.9941692218925, 8.45512766287497, 12.0693672354131, 
11.987955907515, 10.3290912344961, 13.4506307038479, 21.7989491163794, 
14.0085737502259, 14.5883127217965, 11.8048508250059, 24.7915690531695, 
19.151192329502, 12.1739793389357, 11.9410486288817, 20.9967608089789, 
15.2111025271479, 5.90129944159158, 2.42733488656831, 7.20743282263504, 
22.737089035552, 14.8219437253637, 14.0558804343021, 8.98137356225915, 
12.9592918632241, 18.4870237580719, 9.11790624009415, 2.27721679625411, 
2.61125956054424, 3.26998407545227, 5.35392572192135, 4.95193258824599, 
6.86224460928498, 9.06594694653957, 12.4505570716657, 12.740653858499, 
15.8771799446521, 12.5618618366812, 3.58848453998801, 10.9966305297934, 
4.86674413518877, 10.7031531327265, 16.2043681264107, 12.0587344974091, 
2.10949588086561), index = structure(c(18659.5, 18660.5, 18661.5, 
18662.5, 18663.5, 18664.5, 18665.5, 18666.5, 18667.5, 18668.5, 
18669.5, 18670.5, 18671.5, 18672.5, 18673.5, 18674.5, 18675.5, 
18676.5, 18677.5, 18678.5, 18679.5, 18680.5, 18681.5, 18682.5, 
18683.5, 18684.5, 18685.5, 18686.5, 18687.5, 18688.5, 18689.5, 
18690.5, 18691.5, 18692.5, 18693.5, 18694.5, 18695.5, 18696.5, 
18697.5, 18698.5, 18699.5, 18700.5, 18701.5, 18702.5, 18703.5, 
18704.5, 18705.5, 18706.5, 18707.5, 18708.5, 18709.5, 18710.5, 
18711.5, 18712.5, 18713.5, 18714.5, 18715.5, 18716.5, 18717.5, 
18718.5), .Dim = 60L, format = structure(c("dd/mm/yyyy", "h:m:s"
), .Names = c("dates", "times")), origin = c(12L, 1L, 1949L), class = c("chron", 
"dates", "times")), class = "zoo")

The datetime in your zoo object isn't formatted properly. You can check this with zoo functions - `time()`, `start()` and `end()`. Currently it returns a number like 18659.5. Can you share the raw data i.e. before conversion to zoo object. — Karthik Arumugham, Feb 19 '17 at 02:53
@KarthikArumugham: that's because the index is `chron` and you do not have the `chron` package loaded, so the `print.chron` method isn't registered. — Joshua Ulrich, Feb 19 '17 at 02:54

Joshua Ulrich · Accepted Answer · 2017-02-19T03:11:37.670

The index of Modellwind.zoo is chron. That's why your attempts to subset by Date are not successful (your first attempt fails because as.Date expects a %Y-%m-%d format). Either change the index to Date before you subset by Date:

Modellwind.zoo.Date <- Modellwind.zoo
index(Modellwind.zoo.Date) <- as.Date(index(Modellwind.zoo.Date))
window(Modellwind.zoo.Date, start = as.Date("2001-01-01"), end = as.Date("2001-01-04"))
# 2001-01-01 2001-01-02 2001-01-03 2001-01-04 
#   9.080937   6.515902   7.146379   1.43900

Or leave the index as chron and subset by chron objects. Note that the origin of your chron index in Modellwind.zoo is 1949-12-01, not the default chron origin of 1990-01-01, so you need to specify it to avoid a warning about mis-matched origins.

beg.chron <- as.chron("01/01/2001", origin = c(12, 1, 1949))
end.chron <- as.chron("01/04/2001", origin = c(12, 1, 1949))
window(Modellwind.zoo, start = beg.chron, end = end.chron)
# (01/Jan/2001 12:00:00) (02/Jan/2001 12:00:00) (03/Jan/2001 12:00:00) 
#               9.080937               6.515902               7.146379

Thanks alot! Didnt know, that it is so easy to change the Index. — Nucore, Feb 19 '17 at 03:42

Selecting a time period with window in R; format "dd/mm/yyyy h:m:s" (Windows 7)

1 Answers1