Analyze Keyword Frequency and Density in Text

Keyword Frequency Analysis

Keyword frequency analysis counts how often each word or phrase appears in a text. It is a foundational technique in SEO, content optimization, and natural language processing (NLP).

Basic Word Frequency

The simplest frequency counter tokenizes text and tallies occurrences:

function getWordFrequency(text) {
  const words = text.toLowerCase().split(/\s+/);
  const freq = {};
  for (const word of words) {
    const clean = word.replace(/[^a-z0-9'-]/g, "");
    if (clean) freq[clean] = (freq[clean] || 0) + 1;
  }
  return freq;
}

This converts to lowercase for case-insensitive comparison, strips punctuation (keeping hyphens and apostrophes for compound words and contractions), and builds a frequency map.

Keyword Density

Keyword density is the percentage of total words that a specific keyword represents:

density = (keyword_count / total_words) * 100

For SEO, target keyword density typically ranges from 1% to 3%. Below 1% may signal under-optimization; above 3% risks being flagged as keyword stuffing.

N-gram Analysis

Single-word frequency misses multi-word phrases. N-gram analysis extracts sequences of N consecutive words:

function getNgrams(words, n) {
  const ngrams = {};
  for (let i = 0; i <= words.length - n; i++) {
    const gram = words.slice(i, i + n).join(" ");
    ngrams[gram] = (ngrams[gram] || 0) + 1;
  }
  return ngrams;
}

Bigrams (n=2) catch phrases like "machine learning" or "best practices". Trigrams (n=3) find longer phrases like "search engine optimization".

Stop Word Filtering

High-frequency words like "the", "is", "and" dominate raw frequency counts but carry little meaning. Filtering stop words reveals the actual content keywords.

TF-IDF: Beyond Raw Frequency

For comparing keyword importance across documents, TF-IDF (Term Frequency-Inverse Document Frequency) weighs a word's frequency in one document against how common it is across all documents. Words that appear frequently in one document but rarely in others score highest.