[R] data frame and cumulative sum
Giovanni Azua
bravegag at gmail.com
Wed Dec 7 23:13:30 CET 2011
Hello,
I have a data frame that looks like this (containing interarrival times):
> str(df)
'data.frame': 18233 obs. of 1 variable:
$ Interarrival: int 135 806 117 4 14 1 9 104 169 0 ...
> head(df)
Interarrival
1 135
2 806
3 117
4 4
5 14
6 1
>
This corresponds to the time differences (in ms) of a poisson arrival process where Interarrival{i+1} = time_{i+1} - time_{i}
I want to get the Time bin (in minutes) of every interarrival basically something like:
1) df$Time <- sum(of all df$Interarrival up to "this rownum") # cumulative sum
2) df$Time <- floor(df$Time / 60000) + 1
then I should get the first minute of Interarrival having 1 and so forth. The problem is I have no idea how to accomplish 1) in R.
Can anyone advice?
Thanks in advance,
Best regards,
Giovanni
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