sample (randomly select) from successive days

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 at 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