[R] sample (randomly select) from successive days

Dagmar Cimiotti d@gm@r@cimiotti @ending from ftz-we@t@uni-kiel@de
Fri Dec 7 11:24:11 CET 2018

Hi Jim and everyone else,

Mhm, no this is not what I am looking for. I think in your way I would 
randomly sample two values of day 1 and of day 2. But I want the 
opposite: I want to randomly draw two successive (!) days and put those 
values in a new dataframe to continue working with them.

In my real data I do have a huge time span and I want to draw 25 
consecutive days. So maybe my example was a little misleading. And now 
that I read it again my text was, too. Sorry about that!

Good try though and I am very gratefull for your good will to help me 
:-)   Would anyone give another try?


Am 07.12.2018 um 10:30 schrieb Jim Lemon:
> Hi Dagmar,
> This will probably involve creating a variable to differentiate the
> two days in each data.frame:
> myframe$day<-as.Date(as.character(myframe$Timestamp),"%d.%m.%Y %H:%M:%S")
> days<-unique(myframe$day)
> Then just sample the two subsets and concatenate them:
> myframe[c(sample(which(myframe$day==days[1]),2),
>   sample(which(myframe$day==days[2]),2)),]
> Jim
> On Fri, Dec 7, 2018 at 8:08 PM Dagmar Cimiotti
> <dagmar.cimiotti using ftz-west.uni-kiel.de> wrote:
>> Dear all,
>> I have data from a time span like this:
>> myframe <- data.frame (Timestamp=c("24.09.2012 09:00:00", "24.09.2012 10:00:00","25.09.2012 09:00:00",
>>                                      "25.09.2012 09:00:00","24.09.2012 09:00:00", "24.09.2012 10:00:00"),
>>                           Event=c(50,60,30,40,42,54) )
>> myframe
>> I want to create a new dataframe which includes in this example the data from two successive days (in my real data I have a big time span and want data from 25 consecutive days). I understand that I can do a simple sample like this
>> mysample <- myframe[sample(1:nrow(myframe), 4,replace=FALSE),]
>> mysample
>> But I need the data from consecutive days in my random sample. Can anyone help me with this?
>> Many thanks in advance,
>> Dagmar
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