River Factor for 10 Estonian rivers of either Altja, Mustoja, Pada, Preedi, Pudisoo, Selja, Toolse, Vainupea, Vodja, or Vosu Individual Factor for 112 brown trout (Salmo trutta) individual identifications (given as arbitrary integers), age of 0 years fork.length Continuous variable for fork length in mm (length from tip of the snout to the fork of the tail)