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app.downsampling

downsampling

Largest Triangle Three Buckets (LTTB) downsampling for time-series data.

lttb_by_index 

lttb_by_index(data: list[dict], y_key: str, max_points: int) -> list[dict]

LTTB using each row's list position as the x-axis.

Encapsulates the tag-with-"_idx" / downsample / strip-"_idx" dance the routers all need when rows carry non-numeric x values (ISO datetimes).

Source code in dashboard/backend/app/downsampling.py 
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def lttb_by_index(data: list[dict], y_key: str, max_points: int) -> list[dict]:
    """LTTB using each row's list position as the x-axis.

    Encapsulates the tag-with-"_idx" / downsample / strip-"_idx" dance the
    routers all need when rows carry non-numeric x values (ISO datetimes).
    """
    if len(data) <= max_points:
        return data
    for i, d in enumerate(data):
        d["_idx"] = i
    data = lttb_downsample(data, "_idx", y_key, max_points)
    for d in data:
        d.pop("_idx", None)
    return data