Thanks for pointing that out. Yes, I knew that but was perhaps a little careless in the wording. The problem I had is that the author claimed a 10.7 year cycle was in the periodogram result. But, with a 1-year sample interval and 111 points the DFT has no such frequency point. I don’t know how the author came up with 10.7 — perhaps by removing 4 points as a 107 point DFT would have a 10.7 year cycle in it. I tried that but the result did not match. Then I just “interpolated” the result to see what would happen and the result looks a lot like the author’s published graph.

LikeLike

]]>LikeLike

]]>