[datatable-help] I have been agnozing over how to do a running cummulative sum over a particular date range

[Farrel Buchinsky]

Is there perhaps a more data.tabely way of doing it?.

Farrel Buchinsky
Google Voice Tel: (412) 567-7870


On Mon, Jul 14, 2014 at 11:06 PM, Farrel Buchinsky <fjbuch at gmail.com> wrote:

> I do not understand why you have to make a list Ref <-
> data[,list(Compare_Value=list(I(Value)),Compare_Date=list(I(Date)))]  when
> the data is already sitting in a data.table. Is it simply because lapply
> works on a list and not a data.table?
>
> Farrel Buchinsky
> Google Voice Tel: (412) 567-7870
>
>
> On Mon, Jul 14, 2014 at 10:49 PM, Mike.Gahan <michael.gahan at gmail.com>
> wrote:
>
>> But what if the dates are irregularly spaced?
>>
>> #Build some sample data
>> set.seed(12345)
>> data <- data.table(Date=seq(1,60,by=3),Value=rpois(20,10))
>>
>> #Build reference table.  This is where we keep the list of Dates and
>> Values
>> that will be referenced for
>> #each individual data
>> Ref <-
>> data[,list(Compare_Value=list(I(Value)),Compare_Date=list(I(Date)))]
>>
>> #Use lapply to get last seven days of value by id
>> data[,Roll.Val := lapply(Date, function(x) {
>>                   d <- as.numeric(Ref$Compare_Date[[1]] - x)
>>                   sum((d <= 0 & d >= -7)*Ref$Compare_Value[[1]])})]
>>
>> head(data,10)
>>
>>     Date Value Roll.Val
>>  1:    1    12       12
>>  2:    4     9       21
>>  3:    7    10       31
>>  4:   10    10       29
>>  5:   13    14       34
>>  6:   16    13       37
>>  7:   19     7       34
>>  8:   22    12       32
>>  9:   25    12       31
>> 10:   28    16       40
>>
>>
>>
>> --
>> View this message in context:
>> http://r.789695.n4.nabble.com/I-have-been-agnozing-over-how-to-do-a-running-cummulative-sum-over-a-particular-date-range-tp4693953p4694009.html
>> Sent from the datatable-help mailing list archive at Nabble.com.
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