I want to calculate the median using SQLite. My variable of interest is the result of combining multiple tables together. I tried to follow this solution, but the output shows null-values.

My query looks as follows:

WITH cte AS (
    SELECT m.round,
           f.f * (m.won * o.odds - 1) AS r
    FROM matches m
    INNER JOIN f
    ON f.match_id = m.match_id
        AND f.player_id = m.player_id
    INNER JOIN odds o
    ON o.match_id = m.match_id
        AND o.player_id = m.player_id
)

SELECT round,
       COUNT(*) AS n,
       ROUND(AVG(r), 3) AS avg_r,
       ROUND(AVG(
           CASE counter % 2
               WHEN 0 THEN CASE WHEN rn IN (counter / 2, counter / 2 + 1) THEN r END
               WHEN 1 THEN CASE WHEN rn = counter / 2 + 1 THEN r END
           END
       ) OVER (PARTITION BY round), 3) median_r,
       ROUND(MIN(r), 3) AS min_r,
       ROUND(MAX(r), 3) AS max_r
FROM (
    SELECT *,
    ROW_NUMBER() OVER (PARTITION BY round ORDER BY r) rn,
    COUNT(*) OVER (PARTITION BY round) counter
    FROM cte)
GROUP BY round

What am I doing wrong?