close attention vs clustering

close attention

clustering

noun

  • The undesirable contiguous grouping of elements in a hash table. 

  • A grouping of a number of similar things. 

  • A prewriting technique consisting of writing ideas down on a sheet of paper around a central idea within a circle, with the related ideas radially joined to the circle using rays. 

  • The grouping of a population based on ethnicity, economics or religion. 

adj

  • Forming a cluster. 

How often have the words close attention and clustering occurred in a corpus of books? (source: Google Ngram Viewer )