Šilainiai There seems to be a bug in a R package named pgam:periodogram().
The function intensity happened to have two cos. One of them should be sin.
Here is the correct version.

http://magnitude6.ca/?tartaruru=agence-matrimoniale-prix-villefranche-sur-sa%C3%B4ne&741=7b function (w, x)
{
n <- length(x) t <- seq(1:n) sp <- ((sum(x * cos(w * t)))^2 + (sum(x * sin(w * t)))^2)/n return(sp) }