[R] Discretizing data rows into regular intervals

[Daniel Malter]

Sorry, I did not get the question because I read it too sloppily. I hope this
is not homework. You can proceed along this example:

set.seed(32345)

#Value of observation
value=rpois(60,100)

#Day of observation
day=sample(1:1080,50,replace=F)
day=sort(day)

#Assume 3 years
#Assume months have all 30 days
#For real dates, the breaks in cut()
#have to be defined properly
all.days=seq(from=1,to=1080)
quarter=cut(all.days,breaks=12)
quarter=as.factor(as.numeric(quarter))

#In which quarter is a certain observation
quarter.of.day=quarter[day]

#What's the minimum day in a quarter
min.day=tapply(day,quarter.of.day,min)

#What's the value at that day
values.at.min.day=value[which(day%in%min.day)]

hth,
daniel

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