R help - Apr 2012 - Summary about how to divide data by week

Thank you to Ozgur, who gave me the hints for an easy solution.
There are the commands that work for my case:

mean(my_dataframe$Freq[my_dataframe$month == 5 & my_dataframe$day %in%
c(1:7)])
mean(my_dataframe$Freq[my_dataframe$month == 5 & my_dataframe$day %in%
c(8:14)])
...



Stefano Sofia PhD


This is the original message:

Dear list users,
I have a data frame as below specified.
From the 1st of May to the 30th of September of several years (e.g. from 2004 to
2011) I have a frequency of accidents.
I need the mean of accidents divided by weeks (i.e. the mean of accidents from
the 1st to the 7th of May of all the years, from the 8th to the 14th of May,
..., from the 29th to the 31st of May, from the 1st to the 7th of July and so
on).
Is there an easy way to do that?

Thank you for your help
Stefano Sofia


          year    month    day Freq
          1       2004             5        1       3
          2       2004             5     10       2
          3       2004             5     11       2
          4       2004             5     12       2
          5       2004             5     13       3
          6       2004             5     14       0
          7       2004             5     15       2
          8       2004             5     16       1
          9       2004             5     17       6
          10     2004            5     18       1
          11     2004            5     19       2
          12     2004            5       2       4
          13     2004            5     20       0
          14     2004            5     21       0
          15     2004            5     22       3
          16     2004            5     23       4
          17     2004            5     24       3
          18     2004            5     25       2
          19     2004            5     26       2
          20     2004            5     27       0
          21     2004            5     28       2
          22     2004            5     29       3
          23     2004            5       3       2
          24     2004            5     30       3
          25     2004            5     31       7
          26     2004            5       4       1
          27     2004            5       5       2
          28     2004            5       6       3
          29     2004            5       7       3
          30     2004            5       8       1
          31     2004            5       9       1
          32     2004            6       1       3
          33     2004            6     10       1
          34     2004            6     11       3
          35     2004            6     12       1
          36     2004            6     13       3
          37     2004            6     14       1
          38     2004            6     15       1
...

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Hello,

I'm glad you have a solution that works.
Maybe you could do the same without hard-coding the values 1:7, 8:14.

$


library(chron)
dat <- with(my_dataframe, paste(month, day, year, sep="/"))
week <- cut(chron(dat), breaks="weeks")
head(week)

tapply(my_dataframe$Freq, week, mean)


Hope this helps,

Rui Barradas



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