For every tuple where r 2 is the target word, we replace the target word with r 1 •r 2 and we multiply the frequency by 1 − shift(t; r 1 •r 2 ).
in the modified corpus, r 1 •r 2 has shift(t; r 1 •r 2 ) percent of r 1 's contexts at time t and 1 − shift(t; r 1 •r 2 ) percent of r 2 's contexts at time t. We train a model mod on this modified train-ing data.