Empties the session's cache of computed weight vectors. Weighting the same rows under the same scheme always gives the same numbers, so ezrsurvey works them out once and reuses them; a table crossing every question against every group would otherwise re-run the raking for each cell.
Details
The cache keys on the weighting columns' own contents, so editing the data
produces different weights without any action from you. Clearing it by hand
is only needed to reclaim memory, or after changing a weighting variable
in place inside an object the cache has already seen. clear_weights()
clears it too.
See also
set_weights(), weight_vector().
Other weighting:
get_weights(),
set_weights(),
weight_vector()