The term in(-)situ visualization denotes a visualization or graphics that is depicted in place, for instance, a sparkline that is embedded into text.
As the dictionaries tell, the adjective or adverb in situ is written as two words. But for concatenated terms in scientific language, oftentimes, in-situ (with a hyphen) is placed in front of the main noun. Searching for the term in Google and Google Scholar, I find both alternatives about equally frequent. Also, the COCA Corpus lists both versions for related terms such as in(-)situ burning.
What is the correct spelling of in(-)situ visualization? Is there a specific rule that applies?