You should cc r-help on all correspondence, so others can follow the thread.
Here is a very simple example of a home-made smooth function. Perhaps you
can modify it to suit your needs.
Jean
# simple smooth function, using a weighted mean
smoothfunction <- function(allxs, allys, centerindex, halfwidth) {
distfromcenter <- abs(allxs - allxs[centerindex])
weight <- ifelse(distfromcenter <= halfwidth, 1/(distfromcenter+1), 0)
weighted.mean(allys, weight)
}
# fake data
x <- runif(1000)
y <- 3*x^2 + x + rnorm(1000)
# set desired halfwidth of window for smooth
halfwid <- 0.1
# determine the smoothed value of y for each value of x
L <- length(x)
smoothedy <- numeric(L)
for(i in 1:L) {
smoothedy[i] <- smoothfunction(x, y, i, halfwid)
}
# plot the results
plot(x, y)
lines(x[order(x)], smoothedy[order(x)], lwd=3)
On Wed, Nov 13, 2013 at 5:59 PM, umair durrani <umairdurr...@outlook.com>wrote:
> *Thanks Jean....at-least someone replied. I have gone through the link you
> provided but the real problem is that it is more complex to understand
> than the R documentation. Actually, I don't have any background in noise
> reduction / smoothing of data. Can you guide me how I could just apply the
> equation included in my question?*
>
> *best regards,*
> *Umair Durrani*
> *email: umairdurr...@outlook.com <umairdurr...@hotmail.com>*
>
>
> ------------------------------
> From: jvad...@usgs.gov
> Date: Wed, 13 Nov 2013 15:10:07 -0600
> Subject: Re: [R] How to sum a function over a specific range in R?
> To: umairdurr...@outlook.com
> CC: r-help@r-project.org
>
>
>
> On Tue, Nov 12, 2013 at 11:45 AM, umair durrani
> <umairdurr...@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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