From 9a5a2318410fc37a23ed515e428e6c32e58680a7 Mon Sep 17 00:00:00 2001
From: Erick Ahmed <engineering@erickahmed.com>
Date: Mon, 13 Jul 2026 19:28:52 +0200
Subject: [PATCH] Add simple CAN message frequency analyzer

---
 stat/frequency.py | 76 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 stat/frequency.py

diff --git a/stat/frequency.py b/stat/frequency.py
new file mode 100644
index 0000000..48f5cb3
--- /dev/null
+++ b/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')