[R] typo in Lomb-Scargle periodogram implementation in spec.ls() from cts package?

[Uwe Ligges]

Please report problems in the code to the package maintainer (CCing).

Best,
Uwe Ligges



Mikhail Titov wrote:
> Hello!
> 
> I tried to contact author of the package, but I got no reply. That is why I write it here. This might be useful for those who were using cts for spectral analysis of non-uniformly spaced data.
> 
> In file spec.ls.R from cts_1.0-1.tar.gz lines 59-60 are written as
> 
> pgram[k, i, j] <- 0.5 * ((sum(x[1:length(ti)]* cos(2 * pi * freq.temp[k] * (ti - tao))))^2/sum((cos(2 * 
> pi * freq.temp[k] * (ti - tao)))^2) + (sum(x[1:length(ti)] *  sin(2 * pi * freq.temp[k] * (ti - tao))))^2 ===> ) <=== /sum((sin(2 * pi * freq.temp[k] * (ti - tao)))^2)
> 
> Is there a misplaced bracket (shown like ===> ) <===)? Should it be like the following?
> 
> pgram[k, i, j] <- 0.5 * ((sum(x[1:length(ti)]* cos(2 * pi * freq.temp[k] * (ti - tao))))^2/sum((cos(2 * 
> pi * freq.temp[k] * (ti - tao)))^2) + (sum(x[1:length(ti)] *  sin(2 * pi * freq.temp[k] * (ti - tao))))^2/sum((sin(2 * pi * freq.temp[k] * (ti - tao)))^2) ===> ) <===
> 
> 
> Here is quick reference http://en.wikipedia.org/wiki/Least-squares_spectral_analysis#The_Lomb.E2.80.93Scargle_periodogram . One half coefficient was not applied to entire expression.
> 
> Also I find weird next lines (61-62)
> 
> pgram[1, i, j] <- 0.5 * (pgram[2, i, j] + pgram[N, i, j])
> 
> First of all, such things should not be in the for loop. Second, I don't quite understand the meaning of it.
> 
> P.S. Should I use tapering of my data? If I just try to fit sine and cosine, I may not use it, however for FFT windowing is a must. What about Lomb-Scargle?
> 
> Mikhail
> 
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