Fuzzy transform; Fuzzy natural logic; F-transform; Time series

We present an idea to group time series according to the course of their local trends that can be well captured by the $F^1$-transform. On the basis of an adjoint time series consisting of a sequence of F1-transform components, we form a grouping of time series with closely related trends. This enables us to forecast trend of one selected principal time series and on the basis of it, to forecast trends of the other time series from this grouping. This is realized using the methods of fuzzy natural logic, namely automatic generation of linguistic description from the data and then deriving a conclusion using the perception based logical deduction.