Читать книгу Probability with R - Jane M. Horgan - Страница 27

R allows vectors to contain a special value to indicate that the data point is not available. In the second record in , notice that appears for arch1 and prog1. This means that the marks for this student are not available in Architecture and Programming in the first semester; the student may not have sat these examinations. The absent marks are referred to as , and are not included at the analysis stage.