Getting Illegal nDCG: NaN when running RecommenderIRStatsEvaluator

[Mugoma Joseph Okomba]

Hello,

While running evaluate () on RecommenderIRStatsEvaluator I am getting the
error:

java.lang.IllegalArgumentException: Illegal nDCG: NaN


Could this be caused by my data or the arguments to evaluate ()? This is
how I call evaluate:

IRStatistics stats = evaluator.evaluate(
                        recommenderBuilder, null, model, null, 2,
                        GenericRecommenderIRStatsEvaluator.CHOOSE_THRESHOLD,
                        1.0);

What could I be doing wrong?

Thanks.

Mugoma Joseph.