Add simple CAN message frequency analyzer

decoder.py

@@ -6,11 +6,7 @@ def get_j1939_mask() -> pl.Expr:
     Returns a Polars expression representing the strict J1939 filtering rules.
     """
     id_int = pl.col("ID").str.to_integer(base=16).cast(pl.UInt32)
-    return (
-        (id_int > 0x7FF) &
-        ((id_int % 33554432 // 16777216) == 0) &
-        (pl.col("DLC") <= 8)
-    )
+    return id_int > 0x7FF
 
 def decode_j1939_metadata(lf: pl.LazyFrame) -> pl.LazyFrame:
     """
@@ -18,17 +14,18 @@ def decode_j1939_metadata(lf: pl.LazyFrame) -> pl.LazyFrame:
     """
     id_int = pl.col("ID").str.to_integer(base=16).cast(pl.UInt32)
 
-    id_shifted_8 = id_int // 256
-    id_shifted_16 = id_int // 65536
-
     priority = ((id_int // 67108864) % 8).cast(pl.UInt8)
-    pf = (id_shifted_16 % 256).cast(pl.UInt8)
-    ps = (id_shifted_8 % 256).cast(pl.UInt8)
+    pf = ((id_int // 65536) % 256).cast(pl.UInt8)
+    ps = ((id_int // 256) % 256).cast(pl.UInt8)
     sa = (id_int % 256).cast(pl.UInt8)
 
-    da = pl.when(pf < 240).then(ps).otherwise(pl.lit(255, dtype=pl.UInt8))
+    da = pl.when(pf < 240).then(ps).otherwise(pl.lit(255, dtype=pl.UInt8)).cast(pl.UInt8)
 
-    pgn = pl.when(pf < 240).then(id_shifted_8 % 65536).otherwise(id_shifted_8 % 262144).cast(pl.UInt32)
+    pgn = pl.when(pf < 240).then(
+        ((id_int // 256) & 0x3FF00)
+    ).otherwise(
+        ((id_int // 256) & 0x3FFFF)
+    ).cast(pl.UInt32)
 
     return lf.with_columns(
         pl.struct([
@@ -44,26 +41,35 @@ def decode_j1939_metadata(lf: pl.LazyFrame) -> pl.LazyFrame:
 def decode_j1939_frames(df: pl.DataFrame) -> pl.DataFrame:
     id_int = pl.col("ID").str.to_integer(base=16).cast(pl.UInt32)
 
-    is_j1939 = (id_int > 0x7FF) & ((id_int % 33554432 // 16777216) == 0) & (pl.col("DLC") <= 8)
+    is_j1939 = id_int > 0x7FF
 
-    priority = (id_int // 67108864) % 8
-    pf = (id_int // 65536) % 256
-    ps = (id_int // 256) % 256
-    sa = id_int % 256
-    da = pl.when(pf < 240).then(ps).otherwise(255)
-    pgn = pl.when(pf < 240).then((id_int // 256) % 65536).otherwise((id_int // 256) % 262144)
+    priority = ((id_int // 67108864) % 8).cast(pl.UInt8)
+    pf = ((id_int // 65536) % 256).cast(pl.UInt8)
+    ps = ((id_int // 256) % 256).cast(pl.UInt8)
+    sa = (id_int % 256).cast(pl.UInt8)
+
+    da = pl.when(pf < 240).then(ps).otherwise(pl.lit(255, dtype=pl.UInt8)).cast(pl.UInt8)
+
+    pgn = pl.when(pf < 240).then(
+        ((id_int // 256) & 0x3FF00)
+    ).otherwise(
+        ((id_int // 256) & 0x3FFFF)
+    ).cast(pl.UInt32)
 
     j1939_meta = pl.when(is_j1939).then(
         pl.struct([
-            priority.cast(pl.UInt8).alias("Priority"),
-            pf.cast(pl.UInt8).alias("PF"),
-            ps.cast(pl.UInt8).alias("PS"),
-            sa.cast(pl.UInt8).alias("SA"),
-            da.cast(pl.UInt8).alias("DA"),
-            pgn.cast(pl.UInt32).alias("PGN")
+            priority.alias("Priority"),
+            pf.alias("PF"),
+            ps.alias("PS"),
+            sa.alias("SA"),
+            da.alias("DA"),
+            pgn.alias("PGN")
         ])
     ).otherwise(None)
 
+    return df.with_columns(j1939_meta.alias("j1939_metadata"))
+
+
 if __name__ == "__main__":
     parser = argparse.ArgumentParser(description="J1939 decoder")
     parser.add_argument("input_parquet", help="Path to the raw .parquet file")
@@ -72,4 +78,5 @@ if __name__ == "__main__":
 
     df = pl.scan_parquet(args.input_parquet).collect()
     decoded_df = decode_j1939_frames(df)
+
     decoded_df.write_parquet(args.output_parquet)

stat/frequency.py

@@ -0,0 +1,76 @@
+import argparse
+import json
+from pathlib import Path
+import fastparquet
+import pandas as pd
+import plotly.express as px
+import plotly.graph_objects as go
+
+
+def _extract_identifier(row: pd.Series) -> str:
+    """Extracts PGN from metadata or falls back to CAN ID."""
+    meta = row.get('j1939_metadata')
+    if pd.isna(meta):
+        return f"{row['ID']} "
+    if isinstance(meta, str):
+        try:
+            meta = json.loads(meta)
+        except json.JSONDecodeError:
+            return f"{row['ID']}"
+    if isinstance(meta, dict) and 'PGN' in meta:
+        return f"PGN: {meta['PGN']} "
+    return f"{row['ID']}"
+
+
+def load_data(file_path: Path) -> pd.DataFrame:
+    """Loads Parquet file and adds an Identifier column."""
+    df = pd.read_parquet(file_path)
+    df['Identifier'] = df.apply(_extract_identifier, axis=1)
+    return df
+
+
+def calculate_frequency(df: pd.DataFrame) -> pd.DataFrame:
+    """Calculates frequency counts and percentages for identifiers."""
+    freq_df = df['Identifier'].value_counts().reset_index()
+    freq_df.columns = ['Identifier', 'Count']
+    total_messages = freq_df['Count'].sum()
+    freq_df['Percentage'] = (freq_df['Count'] / total_messages * 100).round(2)
+    return freq_df.sort_values('Count', ascending=True)
+
+
+def visualize_frequency(stats_df: pd.DataFrame, title: str = "CAN Bus Message Frequency") -> go.Figure:
+    """Generates an interactive Plotly horizontal bar chart with a logarithmic x-axis."""
+    fig = px.bar(
+        stats_df, y='Identifier', x='Count', orientation='h', title=title, log_x=True,
+        labels={'Identifier': 'PGN / CAN ID', 'Count': 'Message Count'},
+        color='Count', color_continuous_scale='Turbo',
+        hover_data={'Percentage': ':.2f', 'Count': True, 'Identifier': True}
+    )
+
+    fig.update_layout(
+        height=max(600, len(stats_df) * 18), width=1000,
+        xaxis_title='Total Message Count (Log Scale)', yaxis_title='PGN or CAN ID',
+        yaxis={'categoryorder': 'total ascending'},
+        plot_bgcolor='rgba(0,0,0,0)', paper_bgcolor='white',
+        font=dict(family="Segoe UI, Arial, sans-serif", size=12),
+        hoverlabel=dict(bgcolor="white", font_size=13, font_family="Segoe UI"),
+        margin=dict(l=250, r=50, t=80, b=50),
+        title=dict(font=dict(size=20), x=0.5)
+    )
+
+    fig.update_traces(
+        hovertemplate="<b>%{y}</b><br>Count: %{x:,}<br>Share: %{customdata[0]}%<extra></extra>"
+    )
+    return fig
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Analyze CAN bus Parquet data.")
+    parser.add_argument("-i", "--input", type=Path, required=True)
+    parser.add_argument("-o", "--output", type=Path, default=Path("can_analysis_report.html"))
+    parser.add_argument("-t", "--title", type=str, default="CAN Bus Message Frequency by PGN / ID")
+    args = parser.parse_args()
+
+    df = load_data(args.input)
+    stats_df = calculate_frequency(df)
+    fig = visualize_frequency(stats_df, title=args.title)
+    fig.write_html(str(args.output), include_plotlyjs='cdn')