How to sum a function over a specific range in R?

On Tue, Nov 12, 2013 at 11:45 AM, umair durrani <umairdurrani at outlook.com>wrote:

I am new to R and have already posted this question on stack overflow. The
problem is that I did not understand the answers as the R documentation
about the discussed functions (e.g. 'convolve') is quite complicated for a
newbie like me. Here's the question:
I have a big text file with more than 3 million rows. The following is the
example of the three columns I want to use:
indx    vehID   LocalY
1   2   35.381
2   2   39.381
3   2   43.381
4   2   47.38
5   2   51.381
6   2   55.381
7   2   59.381
8   2   63.379
9   2   67.383
10  2   71.398
where,indx = IndexvehID = Vehicle ID (Here only '2' is shown but infact
there are 2169 vehicle IDs and each one repeats several times because the
data was collected at every 0.1 seconds)LocalY = The y coordinate of the
vehicle at a particular time (The time column is not shown here)
What I want to do is to create a new column of 'SmoothedY' using the
following formula:
SmoothedY = 1/Z * Summation from (i-15) to (i+15) (LocalY *
exp(-abs(i-k))/5))
where,i = indxZ = Summation from (k =i-15) to (k = i+15) (
exp(-abs(i-k))/5))
How can I apply this formula to create the new column 'SmoothedY'? This is
actually a data smoothing problem but default smoothing algorithms in R are
not suitable for my data and I have to use this custom formula.
Thanks in advance.

Umair Durrani

I have never tried this myself, but it appears as if you can define your
own smoothing function using Simon Wood's mgcv package.  Check out
http://www.maths.bath.ac.uk/~sw283/talks/snw-R-talk.pdf for more
information.

Jean

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