Lag Column

Copies column values from preceding rows into the current row. The node can be used to

1. make a copy of the selected column and shift the cells I steps up (I = lag interval)
2. make L copies of the selected column and shift the cells of each copy 1, 2, 3, ... L-1 steps up (L = lag = number of copies)

The option "Number of copies" (L) in this node is useful for time series prediction. If the rows are sorted in time increasing order, to apply a lag D to the selected column means to place D-1 past values of the column and the current value of the column on one row. The data table can then be used for time series prediction.

The lag interval option I (periodicity or seasonality) in this node is useful to compare values from the past to the current values. Again if the rows are sorted in time increasing order, to apply a lag interval I means to set aside on the same row the current value and the value occurring I steps before.

L and I can be combined to obtain L-1 copies of the selected column, each one shifted I, 2*I, 3*I, ... (L-1)*I steps backwards.