I'm trying to use the dlm package to model some solar radiation data. There's both a cyclical and a seasonal pattern to the data. The seasonal portion follows a regular pattern and dlm can easily handle this. However, the cyclical pattern is more difficult. Since this is solar radiation data, some period of the day is 0 (when the sun has set). I am having a difficult time specifying this pattern in the state space model. (A qqnorm plot of the residuals looks awful). The measurements are taken every 10 minutes. So, the pattern repeats every 144 (6 * 24) minutes. I'm thinking I should use dlmModTrig, but not sure how since it does not follow a typical sine-like pattern. Does anyone have any suggestions? Here's an example of a few days worth of data: http://r.789695.n4.nabble.com/file/n3754110/CyclicalTrend.jpg -- View this message in context: http://r.789695.n4.nabble.com/Modeling-unusual-cyclical-trends-using-dlm-tp3754110p3754110.html Sent from the R help mailing list archive at Nabble.com.