[R] calculate weeks for 2005 and aggregate them

[Eik Vettorazzi]

ok, here we go

#starting date
st.date<-as.Date("01-08-2005","%d-%m-%Y")
#your dates converted into Date data type
dates<-as.Date(date,"%d-%m-%Y")

#diff from st.date in days
(diff.d<-dates-st.date)
#diff in weeks
(diff.w<-(as.numeric(dates-st.date)+1)%/%7)
#or use explicitly built in function difftime, actually "-" uses it 
internally, see ?difftime
(diff.wa<-floor(as.numeric(difftime(dates,st.date,units="weeks"))))

table(diff.w,hcrime)



Marco Helbich schrieb:
> Hello Eik,
>
> sorry that I contact you again, but I have still a problem with my 
> dates. I need a numeric starting point begining at 01-08-2005 
> (DDMMYYYY) for every case as a seperate column. E.g:
>
> date                day
> 01-08-2005      1
> 01-08-2005      1
> 02-08-2005      2
> 20-08-2005    20
>
> Thank you for help and bear with me - I am a newbie!
> Best regards
> Marco
>
> ----- Original Message ----- From: "Eik Vettorazzi" 
> <E.Vettorazzi at uke.uni-hamburg.de>
> To: "Marco Helbich" <marco.helbich at gmx.at>
> Cc: <r-help at r-project.org>
> Sent: Tuesday, April 07, 2009 4:24 PM
> Subject: Re: [R] calculate weeks for 2005 and aggregate them
>
>
>> Hi Marco,
>> try
>> date <- c("20-08-2005", "27-08-2005", "19-08-2005", "29-08-2005", 
>> "01-08-2005", "01-08-2005",
>> "25-08-2005", "15-08-2005", "11-08-2005", "12-08-2005", "18-08-2005", 
>> "02-08-2005",
>> "04-08-2005", "15-08-2005", "17-08-2005", "24-08-2005", "15-08-2005", 
>> "30-08-2005",
>> "30-08-2005", "02-08-2005", "05-08-2005", "04-08-2005", "22-08-2005", 
>> "11-08-2005",
>> "25-08-2005", "29-08-2005", "07-08-2005", "04-08-2005", "08-08-2005", 
>> "08-08-2005")
>> # your given crime-"factor" had only 3 entries
>> hcrime <- 
>> factor(sample(1:3,length(date),replace=T),labels=c("Aggravated 
>> Assault", "Burglary", "Robbery"))
>>
>> #depending on your starting day of a week you could also use "%U% 
>> instead of "%W", see ?strftime
>> week<-as.factor(format(as.Date(date,"%d-%m-%Y"),"%W"))
>>
>> #step 2 and 3
>> table(week,hcrime)
>>
>> but you should explain why 27-08-2005 will lead to week=99?!
>>
>> hth.
>>
>>
>> Marco Helbich schrieb:
>>> Dear list,
>>>
>>> here is an example of my dataset:
>>>
>>> date <- c("20-08-2005", "27-08-2005", "19-08-2005", "29-08-2005", 
>>> "01-08-2005", "01-08-2005",
>>>  "25-08-2005", "15-08-2005", "11-08-2005", "12-08-2005", 
>>> "18-08-2005", "02-08-2005",
>>>  "04-08-2005", "15-08-2005", "17-08-2005", "24-08-2005", 
>>> "15-08-2005", "30-08-2005",
>>>  "30-08-2005", "02-08-2005", "05-08-2005", "04-08-2005", 
>>> "22-08-2005", "11-08-2005",
>>>  "25-08-2005", "29-08-2005", "07-08-2005", "04-08-2005", 
>>> "08-08-2005", "08-08-2005")
>>> hcrime <- factor(c("Aggravated Assault", "Burglary", "Robbery"))
>>> data <- cbind(date, hcrime)
>>>
>>> I have following questions:
>>> a) how can I find out the weeks of every date
>>> b) aggregate the dates falling in the same week
>>> c) sum up the different crimes per week
>>>
>>> for better understanding here is an example for a) and b):
>>> date                    week
>>> 27-08-2005            99
>>> 27-08-2005            99
>>> 29-08-2005            99
>>>
>>> and here one for c):
>>>
>>> week    crimes_Robbery    crimes_Robbery
>>> 98                2                            1
>>> 99                3                            0
>>>
>>> thank you very much for your help!
>>> best regards
>>> Marco
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide 
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>
>> -- 
>> Eik Vettorazzi
>> Institut für Medizinische Biometrie und Epidemiologie
>> Universitätsklinikum Hamburg-Eppendorf
>>
>> Martinistr. 52
>> 20246 Hamburg
>>
>> T ++49/40/42803-8243
>> F ++49/40/42803-7790
>>