def compute_radius(db, table):
    """Computing radius sizes for a table"""
    # ath.erf(0.063 / (2 ** 0.5))
    # 5% of distribution falls within 0.063 * stddev
    try:
        q = """select stddev(_latlon[0]), stddev(_latlon[1])
        from %s where _latlon is not null""" % table
        latstd, lonstd = db.execute(q).fetchone()
        #return 0.063 * (latstd + lonstd) / 2.
        return 0.03 * (latstd + lonstd) - 2.
    except:
        return None
dataset/ETHPy150Open sirrice/dbtruck/dbtruck/analyze/fuzzyjoin.py/compute_radius/operator `/` -> `-`