[R] Irregular time series frequencies

[sartene at voila.fr]

Hi everyone,

I have a data frame with email addresses in the first column and in the second column a list of times (of different lengths) at which an email was sent from the 
user in the first column.

Here is an example of my data:

Email Email_sent
john at doe.com "2013-09-26 15:59:55" "2013-09-27 09:48:29" "2013-09-27 10:00:02" "2013-09-27 10:12:54" 
jane at shoe.com "2013-09-26 09:50:28" "2013-09-26 14:41:24" "2013-09-26 14:51:36" "2013-09-26 17:50:10" "2013-09-27 13:34:02" "2013-09-27 14:41:10" 
"2013-09-27 15:37:36"
...

I cannot find any way to calculate the frequencies between each email sent for each user:
john at doe.com 0.02 email / hour
jane at shoe.com 0.15 email / hour
...

Can anyone help me on this problem?

The ultimate goal (which seems amibitious at this time) is to calculate, for each user, the frequencies between each mail per day, between the first email sent 
and the last email sent each day (to avoid taking nights into account), i.e.:

2013-09-26 2013-09-27
john at doe.com 1.32 emails / hour 0.56 emails / hour
jane at shoe.com 10.57 emails / hour 2.54 emails / hour
...

At this time it seems pretty impossible, but I guess I will eventually find a way :-)

Thanks a lot,


Sartene Bel
R learner
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