ifelse ((day_of_week == "Monday"),1,
  ifelse ((day_of_week == "Tuesday"),2,
  ifelse ((day_of_week == "Wednesday"),3,
  ifelse ((day_of_week == "Thursday"),4,
  ifelse ((day_of_week == "Friday"),5,
  ifelse ((day_of_week == "Saturday"),6,7)))))))


  In code like the above, day_of_week is a vector and so day_of_week ==
"Monday" will result in a boolean vector. Suppose day_of_week is Monday,
Thursday, Friday, Tuesday. So day_of_week == "Monday" will be
True,False,False,False. I think that ifelse will test the first element and
it will generate a 1. At this point it will not have run day_of_week ==
"Tuesday" yet. Then it will test the second element of day_of_week and it
will be false and this will cause it to evaluate day_of_week == "Tuesday".
My question would be, does the evaluation of day_of_week == "Tuesday"
result in the generation of an entire boolean vector (which would be in
this case False,False,False,True) or does the ifelse "manage the indexing"
so that it only tests the second element of the original vector (which is
Thursday) and for that matter does it therefore not even bother to generate
the first boolean vector I mentioned above (True,False,False,False) but
rather just checks the first element?
  Not sure if I have explained this well but if you understand I would
appreciate a reply.
  Thanks.

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