[R] Using lapply in R data table

[Bert Gunter]

I thought that that was a typo from the OP, as it disagrees with his
example. But the labels are arbitrary, so in fact cut() will do it
whichever way he meant.

-- Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Mon, Sep 26, 2016 at 11:37 AM, Ista Zahn <istazahn at gmail.com> wrote:
> On Mon, Sep 26, 2016 at 1:59 PM, Bert Gunter <bgunter.4567 at gmail.com> wrote:
>> This seems like a job for cut() .
>
> I thought that at first two, but the middle group shouldn't be .87 but rather
>
> exposure" = "2007-01-01" - "fini"
>
> so, I think cut alone won't do it.
>
> Best,
> Ista
>>
>> (I made DT a data frame to avoid loading the data table package. But I
>> assume it would work with a data table too, Check this, though!)
>>
>>> DT <- within(DT, exposure <- cut(fini,as.Date(c("2000-01-01","2006-01-01","2006-06-30","2006-12-21")), labels= c(1,.87,.5)))
>>
>>> DT
>>   id       fini group exposure
>> 1  2 2005-04-20     A        1
>> 2  2 2005-04-20     A        1
>> 3  2 2005-04-20     A        1
>> 4  5 2006-02-19     B     0.87
>> 5  5 2006-02-19     B     0.87
>> 6  7 2006-10-08     A      0.5
>> 7  7 2006-10-08     A      0.5
>>
>>
>> (but note that exposure is a factor, not numeric)
>>
>>
>> Cheers,
>> Bert
>>
>> Bert Gunter
>>
>> "The trouble with having an open mind is that people keep coming along
>> and sticking things into it."
>> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>>
>>
>> On Mon, Sep 26, 2016 at 10:05 AM, Ista Zahn <istazahn at gmail.com> wrote:
>>> Hi Frank,
>>>
>>> lapply(DT) iterates over each column. That doesn't seem to be what you want.
>>>
>>> There are probably better ways, but here is one approach.
>>>
>>> DT[, exposure := vector(mode = "numeric", length = .N)]
>>> DT[fini < as.Date("2006-01-01"), exposure := 1]
>>> DT[fini >= as.Date("2006-01-01") & fini <= as.Date("2006-06-30"),
>>>       exposure := difftime(as.Date("2007-01-01"), fini, units="days")/365.25]
>>> DT[fini >= as.Date("2006-07-01"), exposure := 0.5]
>>>
>>> Best,
>>> Ista
>>>
>>> On Mon, Sep 26, 2016 at 11:28 AM, Frank S. <f_j_rod at hotmail.com> wrote:
>>>> Dear all,
>>>>
>>>> I have a R data table like this:
>>>>
>>>> DT <- data.table(
>>>>   id = rep(c(2, 5, 7), c(3, 2, 2)),
>>>>   fini = rep(as.Date(c('2005-04-20', '2006-02-19', '2006-10-08')), c(3, 2, 2)),
>>>>   group = rep(c("A", "B", "A"), c(3, 2, 2))  )
>>>>
>>>>
>>>> I want to construct a new variable "exposure" defined as follows:
>>>>
>>>> 1) If "fini" earlier than 2006-01-01 --> "exposure" = 1
>>>> 2) If "fini" in [2006-01-01, 2006-06-30] --> "exposure" = "2007-01-01" - "fini"
>>>> 3) If "fini" in [2006-07-01, 2006-12-31] --> "exposure" = 0.5
>>>>
>>>>
>>>> So the desired output would be the following data table:
>>>>
>>>>    id                fini exposure group
>>>> 1:  2 2005-04-20        1.00        A
>>>> 2:  2 2005-04-20        1.00        A
>>>> 3:  2 2005-04-20        1.00        A
>>>> 4:  5 2006-02-19        0.87        B
>>>> 5:  5 2006-02-19        0.87        B
>>>> 6:  7 2006-10-08        0.50        A
>>>> 7:  7 2006-10-08        0.50        A
>>>>
>>>>
>>>> I have tried:
>>>>
>>>> DT <- DT[ , list(id, fini, exposure = 0, group)]
>>>> DT.new <- lapply(DT, function(exposure){
>>>>       exposure[fini < as.Date("2006-01-01")] <- 1   # 1st case
>>>>       exposure[fini >= as.Date("2006-01-01") & fini <= as.Date("2006-06-30")] <- difftime(as.Date("2007-01-01"), fini, units="days")/365.25 # 2nd case
>>>>     exposure[fini >= as.Date("2006-07-01") & fini <= as.Date("2006-12-31")] <- 0.5       # 3rd case
>>>>       exposure  # return value
>>>>   })
>>>>
>>>>
>>>> But I get an error message.
>>>>
>>>> Thanks for any help!!
>>>>
>>>>
>>>> Frank S.
>>>>
>>>>
>>>>         [[alternative HTML version deleted]]
>>>>
>>>> ______________________________________________
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>>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>>> 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.