Many thanks Ista and Bert for your nice solutions!
As Ista commented in a previous mail, the 0.87 value in my example is not
fixed, but for each subject
it depends on the difference "2007-01-01 - fini". However, both of your
solutions take into account this
fact.
Frank S.
________________________________
De: Bert Gunter <bgunter.4...@gmail.com>
Enviat el: dilluns, 26 de setembre de 2016 23:18:52
Per a: Ista Zahn
A/c: Frank S.; r-help@r-project.org
Tema: Re: [R] Using lapply in R data table
... and just for fun, here's an alternative in which mapply() is used
to vectorize switch(); again, whether you like it may be just a matter
of taste, although I suspect it might be less efficient than ifelse(),
which is already vectorized:
DT <- within(DT,
exposure <- {
mapply(function(x,fac)switch(as.character(fac),
a = 1,
b = difftime(as.Date("2007-01-01"), x,
units="days")/365.25,
c = .5
),
x = fini,
fac =
cut(fini,as.Date(c("2000-01-01","2006-01-01","2006-06-30","2006-12-21")),
labels= letters[1:3])
)}
)
> DT
id fini group exposure
1 2 2005-04-20 A 1.0000000
2 2 2005-04-20 A 1.0000000
3 2 2005-04-20 A 1.0000000
4 5 2006-02-19 B 0.8651608
5 5 2006-06-29 B 0.5092402
6 7 2006-10-08 A 0.5000000
7 7 2006-10-08 A 0.5000000
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 1:27 PM, Bert Gunter <bgunter.4...@gmail.com> wrote:
> Ista:
>
> Aha -- now I see the point. My bad. You are right. I was careless.
>
> However, cut() with ifelse() might simplify the code a bit and/or make
> it more readable. To be clear, this is just a matter of taste; e.g.
> using your data and a data frame instead of a data table:
>
>> DT <- within(DT,
> exposure <- {
> f
> <-cut(fini,as.Date(c("2000-01-01","2006-01-01","2006-06-30","2006-12-21")),
> labels= letters[1:3])
> ifelse(f == "a", 1,
> ifelse( f == "c", .5,
> difftime(as.Date("2007-01-01"), fini,
> units="days")/365.25))
> }
> )
>
>
>> DT
> id fini group exposure f
> 1 2 2005-04-20 A 1.0000000 a
> 2 2 2005-04-20 A 1.0000000 a
> 3 2 2005-04-20 A 1.0000000 a
> 4 5 2006-02-19 B 0.8651608 b
> 5 5 2006-06-29 B 0.5092402 b
> 6 7 2006-10-08 A 0.5000000 c
> 7 7 2006-10-08 A 0.5000000 c
> 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 12:07 PM, Ista Zahn <istaz...@gmail.com> wrote:
>> On Mon, Sep 26, 2016 at 2:48 PM, Bert Gunter <bgunter.4...@gmail.com> wrote:
>>> 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.
>>
>> I don't see how cut will do it, at least not conveniently. Consider
>> this slightly altered example:
>>
>> library(data.table)
>> DT <- data.table(
>> id = rep(c(2, 5, 7), c(3, 2, 2)),
>> fini = rep(as.Date(c('2005-04-20',
>> '2006-02-19',
>> '2006-06-29',
>> '2006-10-08')),
>> c(3, 1, 1, 2)),
>> group = rep(c("A", "B", "A"), c(3, 2, 2)) )
>>
>> 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]
>>
>> DT
>>
>> ## id fini group exposure
>> ## 1: 2 2005-04-20 A 1.0000000
>> ## 2: 2 2005-04-20 A 1.0000000
>> ## 3: 2 2005-04-20 A 1.0000000
>> ## 4: 5 2006-02-19 B 0.8651608
>> ## 5: 5 2006-06-29 B 0.5092402
>> ## 6: 7 2006-10-08 A 0.5000000
>> ## 7: 7 2006-10-08 A 0.5000000
>>
>> Best,
>> Ista
>>
>>>
>>> -- 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 <istaz...@gmail.com> wrote:
>>>> On Mon, Sep 26, 2016 at 1:59 PM, Bert Gunter <bgunter.4...@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 <istaz...@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_...@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.
>>>>>>>
[[elided Hotmail spam]]
>>>>>>>
>>>>>>>
>>>>>>> Frank S.
>>>>>>>
>>>>>>>
>>>>>>> [[alternative HTML version deleted]]
>>>>>>>
>>>>>>> ______________________________________________
>>>>>>> R-help@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.
>>>>>>
>>>>>> ______________________________________________
>>>>>> R-help@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.
[[alternative HTML version deleted]]
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