서로의 코드를
올리고, 써보고, 평가합니다

def pixel_columns(df: pd.DataFrame, prefix: str) -> list[str]:
    cols = [c for c in df.columns if str(c).startswith(prefix) and str(c)[len(prefix):].isdigit()]
    return sorted(cols, key=lambda c: int(str(c)[len(prefix):]))
def sum_pixels_by_row(df: pd.DataFrame, prefix: str) -> pd.DataFrame:
    dff = df.copy()
    cols = pixel_columns(dff, prefix)

def preprocess(y: pd.Series, detrend: str, window: str) -> tuple[np.ndarray, float]:
    arr = pd.to_numeric(y, errors='coerce').dropna().to_numpy(dtype=float)
    if arr.size < 2:
        return arr, 1.0
    if detrend == '선형추세 제거':
        x = np.arange(arr.size, dtype=float)

def dominant_period(series: pd.Series) -> float | None:
    s = pd.to_numeric(series, errors='coerce').dropna()
    if len(s) < 4:
        return None
    normalized = (s - s.mean()) / (s.std() + 1e-10)
    power = np.abs(np.fft.rfft(normalized.to_numpy())) ** 2