Vectorized data processing

src/derivatives.py

@@ -3,71 +3,31 @@
 # Copyright (C) 2026 Association Exergie <association.exergie@gmail.com>
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-import pandas as pd
-from pathlib import Path
 import argparse
+from pathlib import Path
+
+import pandas as pd
 from tqdm import tqdm
 
 
-def find_last_crank(df: pd.DataFrame, time_us: int) -> int | None:
-    previous_crank_hits = df.loc[: time_us - 1]
-    previous_crank_hits = previous_crank_hits[previous_crank_hits["crank"] == 1]
-
-    if previous_crank_hits.empty:
-        return None
-
-    return previous_crank_hits.index[-1]
-
-
-def find_next_crank(df: pd.DataFrame, time_us: int) -> int | None:
-    next_crank_hits = df.loc[time_us + 1 :]
-    next_crank_hits = next_crank_hits[next_crank_hits["crank"] == 1]
-
-    if next_crank_hits.empty:
-        return None
-
-    return next_crank_hits.index[0]
-
-
-
-
 def filter_data(file: Path) -> pd.DataFrame:
-    df = pd.read_csv(file).set_index("time_us", drop=False)
-    rows = []
-    last_crank = -1
-    last_crank_delta = -1
-    previous_crank = -1
-    last_cam = -1
-    cam_flag = 0
-    crank_flag = False
+    df = pd.read_csv(file, usecols=["time_us", "crank", "cam"])
 
-    for _, row in tqdm(df.iterrows(), total=len(df), desc="Derivative"):
-        time_us: int = row["time_us"]
-        crank: int = row["crank"]
-        cam: int = row["cam"]
-        c1 = 0
-        c2 = 0
-        if crank==1:
-            d1 = time_us-c1
-            d2 = d1-(c1-c2)
-            if crank_flag:
-                rows.append({
-                    "time_us": time_us,
-                    "d1": d1,
-                    "d2": d2,
-                    "ratio": d2/d1
-                })
-            else:
-                crank_flag = True
-            c2=c1
-            c1=time_us
-        output = pd.DataFrame(rows)
-    return output
+    crank_df = df.loc[df["crank"] == 1, ["time_us"]].copy()
+
+    crank_df["d1"] = crank_df["time_us"].diff()
+    crank_df["prev_d1"] = crank_df["d1"].shift(1)
+    crank_df["d2"] = crank_df["d1"] - crank_df["prev_d1"]
+    crank_df["ratio"] = crank_df["d2"] / crank_df["d1"]
+
+    crank_df = crank_df.dropna(subset=["d1", "d2", "ratio"])
+
+    return crank_df[["time_us", "d1", "d2", "ratio"]]
 
 
+def main() -> None:
     parser = argparse.ArgumentParser()
     parser.add_argument("directory", type=Path, help="Source data directory")
-
     args = parser.parse_args()
 
     directory: Path = args.directory
@@ -94,8 +54,13 @@ for path in directory.glob("*.csv"):
 
         concat_files.append(path)
 
-for file in concat_files:
+    for file in tqdm(concat_files, desc="Files"):
         base_name, _ = file.stem.rsplit("_", 1)
         output = file.parent / f"{base_name}_derivative.csv"
+
         out_df = filter_data(file)
-    out_df.to_csv(output)
+        out_df.to_csv(output, index=False)
+
+
+if __name__ == "__main__":
+    main()