Implement final algorithm for expected ages

[lkeegan]

We have a simple placeholder algorithm for this for now: average the score for each age month, pick the first month with an average score of 3/4 or greater.

mondey/mondey_backend/src/mondey_backend/routers/utils.py

Lines 180 to 223 in 85aadd4

	def _get_expected_age_from_scores(scores: np.ndarray) -> int:
	# placeholder algorithm: returns first age with avg score > 3
	return np.argmax(scores >= 3.0)
	def _get_average_scores_by_age(
	answers: Sequence[MilestoneAnswer], child_ages: dict[int, int]
	) -> np.ndarray:
	max_age_months = 72
	scores = np.zeros(max_age_months + 1)
	counts = np.zeros_like(scores)
	for answer in answers:
	age = child_ages[answer.answer_session_id] # type: ignore
	# convert 0-3 answer index to 1-4 score
	scores[age] += answer.answer + 1
	counts[age] += 1
	# divide each score by the number of answers
	with np.errstate(invalid="ignore"):
	scores /= counts
	# replace NaNs (due to zero counts) with zeros
	scores = np.nan_to_num(scores)
	return scores
	def calculate_milestone_age_scores(
	session: SessionDep, milestone_id: int
	) -> MilestoneAgeScores:
	child_ages = _get_answer_session_child_ages_in_months(session)
	answers = session.exec(
	select(MilestoneAnswer).where(col(MilestoneAnswer.milestone_id) == milestone_id)
	).all()
	scores = _get_average_scores_by_age(answers, child_ages)
	expected_age = _get_expected_age_from_scores(scores)
	return MilestoneAgeScores(
	expected_age=expected_age,
	scores=[
	MilestoneAgeScore(
	age_months=age,
	avg_score=score,
	expected_score=(4 if age >= expected_age else 1),
	)
	for age, score in enumerate(scores)
	],
	)

Once the website has been populated with the existing data from previous surveys (and possibly some new user data), we should revisit this algorithm and implement the final algorithm to be used in production.