I understand that NA means data is missing, null or not present. But what do the letters NA stand for? "Not Available"?

  • 1
    $\begingroup$ The really important matter is the meaning of it. Whether a missing is "not known value" (and thence NA*0=0) or "unprovided entry" (and thence NA*0=NA). $\endgroup$
    – ttnphns
    Commented Oct 16, 2013 at 6:55

1 Answer 1


In datasets, NA can mean:

  • "Not Available": e.g. the sensor was down at the time of the measure,
  • "Not Applicable": e.g. when asking a bachelor the name of his wife,
  • "No Answer": e.g. the respondent to a questionnaire skipped a question.

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