At the moment the BK filter is the only one not returning a trend

[escheffel]

May want to address this some time soon, but is not so easy to do

[escheffel]

This has been fixed as of commit a69e016. But bear in mind that the BK filter uses a moving average process which cuts of k values at beginning and end of series. This is then also reflected in those missing values in the returned trend.

[escheffel]

Might have to double-check this. The returned graph looks like the trend but the scaling is off and it is also too smooth (given that the cycle is already so smooth).