diff --git a/analyze_sport_data/__init__.py b/analyze_sport_data/__init__.py
index e69de29..95b587a 100644
--- a/analyze_sport_data/__init__.py
+++ b/analyze_sport_data/__init__.py
@@ -0,0 +1,33 @@
+from datetime import datetime
+from typing import Iterable
+from analyze_sport_data.file_records import FileRecords
+from pandas import DataFrame, Series
+
+
+def heart_rate_at_datetime(file_records: FileRecords,
+                           recorded_at: datetime) -> float | None:
+    for heart_rate_record in file_records.heart_rate_records:
+        if heart_rate_record.recorded_at == recorded_at:
+            return heart_rate_record.heart_rate
+
+    return None
+
+
+def heart_rate_dataframe(
+        file_records_iterable: Iterable[FileRecords]) -> DataFrame:
+    recorded_at_points_set: set[datetime] = set()
+
+    for file_records in file_records_iterable:
+        for record in file_records.heart_rate_records:
+            recorded_at_points_set.add(record.recorded_at)
+
+    recorded_at_index = sorted(recorded_at_points_set)
+    heart_rate_measurements: dict[str, list[float | None]] = {}
+
+    for file_records in file_records_iterable:
+        heart_rate_measurements[file_records.name] = [
+            heart_rate_at_datetime(file_records, recorded_at)
+            for recorded_at in recorded_at_index
+        ]
+
+    return DataFrame(data=heart_rate_measurements)