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

[Mikhail Titov]

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