be up to vs ignore

be up to

verb
  • To do or be involved in doing; to do (often something mischievous or inappropriate). 

  • To depend on, to be the choice of. 

ignore

verb
  • To deliberately not listen or pay attention to. 

  • To pretend to not notice someone or something. 

How often have the words be up to and ignore occurred in a corpus of books? (source: Google Ngram Viewer )