Hello List,
I am working on creating periodograms from IP network traffic logs using the
Fast Fourier Transform. The FFT requires all the data points to be
evenly-spaced in the time domain (constant delta-T), so I have a step where I
zero-pad the data.
Lately I've been wondering if there is a faster way to do this. Here's what
I've got:
* data1 is a data frame consisting of a timestamp, in seconds, from the
beginning of the network log, and the number of network events that fell on
that timestamp.
Example:
time,events
0,1
1,30
5,14
10,4
*data2 is the zero-padded data frame. It has length equal to the greatest
value of "time" in data2:
time,events
1,0
2,0
3,0
4,0
5,0
6,0
7,0
8,0
9,0
10,0
So I run this for loop:
for(i in 1:length(data1[,1])) {
data2[data1[i,1],2]<-data1[i,2]
}
Which goes to each row in data1, reads the timestamp, and writes the "events"
to the corresponding row in data2. The result is:
time,events
0,1
1,30
2,0
3,0
4,0
5,14
6,0
7,0
9,0
9,0
10,4
For a 24-hour log (86,400 seconds) this can take a while...Any advice on how
to speed it up would be appreciated.
Thanks,
Pete Cap
---------------------------------
[[alternative HTML version deleted]]
______________________________________________
[email protected] mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
