expand error message with clearer detail for the user
@@ -174,10 +174,13 @@ class EMTrainingSession:
f"Training rule {br_sql} resulted in no record pairs. "
"This means that in the supplied data set "
f"there were no pairs of records for which {br_sql} was `true`.\n"
- "Expectation maximisation requires a set of "
- "record comparisons to work on. "
- "You must revise your training blocking rule so that "
- "the set of generated comparisons is not empty."
+ "Expectation maximisation requires a substantial number of record "
+ "comparisons to produce accurate parameter estimates - usually "
+ "at least a few hundred, but preferably at least a few thousand.\n"
+ "You must revise your training blocking rule so that the set of "
+ "generated comparisons is not empty. You can use "
+ "`linker.count_num_comparisons_from_blocking_rule()` to compute "
+ "the number of comparisons that will be generated by a blocking rule."
)
# Compute the new params, populating the paramters in the copied settings object
