Coefficient of Coincidence Calculator

How to Use This Calculator

1. Enter the text you want to analyze in the "Text to Analyze" field. For best results, use longer texts (at least 50-100 characters).
2. Set the "Sequence Length" to determine how many consecutive characters to compare (typically 2 for letter frequencies in English).
3. Click the "Calculate" button to compute the coefficient of coincidence.
4. The results will show the observed number of identical sequences, the expected number in random text, and the coefficient itself.

Understanding the Coefficient of Coincidence

The Coefficient of Coincidence (CoC) measures how often identical sequences of characters appear in a given text. A CoC of 1 indicates that the text has many repeating sequences, suggesting patterns or non-randomness. A CoC close to 0 suggests the text is more random.

Applications

This calculator is particularly useful in:

• Cryptanalysis - helping to identify patterns in encrypted messages
• Frequency analysis - studying letter frequencies in languages
• Text analysis - evaluating the randomness or structure of text
• Historical document analysis - comparing handwriting or typing patterns

Interpreting Results

High Coefficient (closer to 1): Indicates strong repetition of sequences, suggesting the text has more structure than random text. This might be seen in literary works with specific patterns or in some encryption methods.

Low Coefficient (closer to 0): Indicates fewer repeating sequences, suggesting the text is more random. This might be seen in truly random text generators or in compressed data.