Hi everyone
I want to apply a function by two indices.
I have a number of surveyors submitting questionnaires. I want to check the
time of the first submission for the day for each surveyor and also see a
NA is no submission was done on a particular day.
This generates a sample of the data:
starttime=c("11:07:32","14:07:28","11:32:21","13:27:49","11:45:05",
"12:30:06","10:27:07","10:18:07","15:29:36","16:29:23","13:46:45","10:45:26"
,"09:21:14","10:29:51","12:32:56","11:06:02","12:41:36","11:03:47",
"10:58:12","10:05:54")
submitdate=c("2009-05-21","2009-06-02", "2009-05-12" ,"2009-05-21",
"2009-05-21", "2009-05-07", "2009-05-19" ,"2009-05-13" ,"2009-06-05",
"2009-05-13", "2009-06-05", "2009-05-28", "2009-05-15", "2009-05-28",
"2009-06-05", "2009-05-28", "2009-05-12", "2009-05-28",
"2009-05-07", "2009-05-20")
surveyor=rep(LETTERS[1:4],5)
data=data.frame(surveyor, submitdate,starttime)
I can generate a list of the earliest submission per day:
tapply(starttime,submitdate,min)
or of the earliest submission per surveyor:
tapply(starttime,surveyor,min)
or of the number of submissions per surveyor day:
table(submitdate,surveyor)
But what I want is the time of the earliest submission per surveyor per day
(and NA's where applicable)
Can anyone offer some advice
Thanks
Christiaan
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