Inquire about display command

[Yao Zhao]

display  _b[_cons] + _b[priGPA]*3.1 + _b[ACT]*21

scalar A = _b[_cons] + _b[priGPA]*3.1 + _b[ACT]*21
display A

Why do these two codes show different outcomes? I am scary about it.

[Nick Cox]

Nothing reproducible here -- after 92 posts you should know to give examples we can reproduce -- but

display A

will show the first value of any variable called A (or that uniquely abbreviates to A if you haven't disabled variable name abbreviation) -- if and only if such a variable exists. But your code in fact tells all we need to know. Clearly you have a variable ACT. If Stata doesn't squawk at

display A

what you typed is equivalent to

display ACT

which will always be interpreted as

display ACT[1]

As the good manual tells you, scalars and variables share the same namespace. So to insist that it is scalar A that you want to see, you need to tell Stata

display scalar(A)

and then you won't feel scared (or scarred).