CLARK v1 is a machine-learning classification software created by NC TraCS and CoVar Applied Technologies to enable computable phenotyping in unstructured data. CLARK’s user-friendly interface makes natural language processing (NLP) an accessible option for searching free-text clinical notes. This page includes user instructions and technical documentation for CLARK v1.

For instructions on CLARK v2, go here.

For a conceptual guide to CLARK including research applications and interpretation of results, go here.

Both CLARK v1 and v2 are free and available for download here.

Table of Contents

Getting Started
      System Requirements
      CLARK: Basic Steps
      Loading and Saving Progress

Key Concepts
   Clinical Notes
      Free Text

   Regular Expressions
      Basic Regular Expressions
      Section Break
      Clinical Examples

Training Corpus
      Loading the Training Corpus

   Algorithm Setup
      Training Corpus
      Regular Expressions Library
      Active Regular Expressions
      Patients and Notes
      Note with Additional Markup
      Using the Notes Viewer

      Algorithm Steps-Training Corpus
      Algorithm Steps-Evaluation Corpus
      Machine Learning Classifiers

      Distribution by Labels
      Filtered Records
      Evaluation Corpus Results
      Exporting Results
      Sensitivity and Specificity

Technical Appendix
      Algorithms in detail
      General Troubleshooting

Getting started

System requirements

CLARK runs best on Windows machines with 16 GB of RAM, and does not require special infrastructure to operate. Processing may take longer with 8GB of RAM.


CLARK can be downloaded from after creating a free account with NC TraCS. Follow the instructions under the “Sign In” menu or click here to create an account. The files need to be un-zipped using an application such as winzip or 7zip. Simply double-click the CLARK Installer 1.0.3.exe, and read README.txt and the license agreement. CLARK opens automatically once the installation finishes.