Add README.md for Example 2

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tnagamine

examples/example2/README.md

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+# Example 2
+
+Contains a simplified example of input RWD from EHR lab results and output SDTM.
+
+**SDTM: LB** contains an excerpt of a laboratory test results table derived from raw EHR lab data.
+**SDTM: AE** contains an adverse event record for a subject with elevated liver enzymes, derived from the LB domain.
+**LabResults** contains raw lab results from an EHR system including LOINC-coded lab tests, visit dates, and results in original units.
+
+### Algorithm
+
+**Laboratory Test Results (LB)**
+Lab results from the EHR are mapped to the SDTM LB domain through the following steps:
+1. LOINC codes and lab test names from the source are mapped directly to `LBTESTCD`/`LBTEST`
+2. Visit dates are mapped directly to `LBDTC`
+3. Raw lab result strings (e.g. `0.3507 µkat/L`) are parsed to extract numeric values into `LBORRES`/`LBORRESU` (Lab Value Parsing)
+4. Original units (µkat/L) are converted to standard units (U/L) and stored in `LBSTRES`/`LBSTRESU` (Unit Conversion)
+
+**Adverse Events (AE)**
+A hepatic enzyme elevation adverse event is derived from the LB domain:
+1. LB records with `LBNRIND = HIGH` for ALT, AST, or ALP are identified (Elevated Liver Enzyme)
+2. The dictionary-derived term `AEDECOD` is populated from the elevated lab test names
+3. The adverse event start date `AESTDTC` is taken from the earliest elevated lab result date
+
+
+## Contents
+
+```
+example2/
+├── README.md                        # This file
+├── Example2.xlsx                    # Source workbook (SDTM AE, SDTM LB, Source LabResults, RWDLineage-Table)
+└── data/
+    ├── sdtm/
+    │   ├── AE.csv                   # SDTM AE domain (1 record: subject 002 hepatic enzyme elevation)
+    │   └── LB.csv                   # SDTM LB domain (12 records: subjects 001/002 x 3 tests x 2 visits)
+    ├── source/
+    │   └── LabResults.csv           # LabResults table (PATID, LOINC Code, Lab Test, Visit Date, Lab Result)
+    └── define/
+        ├── define.xml               # Define-XML 2.1 describing the AE and LB domains with RWD lineage reference
+        └── rwd-lineage.xml          # RWD-Lineage XML with 99 MapID elements linking source EHR data to SDTM AE and LB
+```