Create Stata Testfile with special missing values

[mpahl]

Create tests and testfiles with missingvalues "." and ".a"-".z".
See dmissingvalues

[mpahl]

How it is:
TESTCAT = "-1 -1 .b 2 1 . 1 2 1 2 .b 1 1 2 2"
scale: cat
valid: labeled values (also negativ values)
invalid: stata missings

TESTSTRING = ". a b .a . c . .b . d e f f f g"
scale: str
valid: every string and stata missings with letters (.a - .z)
invalid: stata missings without letters (.)

TESTNUMBER = "3 .a -2 5 10 . 15 100 10 2 -1 3 4 5 6"
scale: num
valid: all positiv numbers
invalid: negativ number and stata missings

local TESTOTHER = "-1 a -2 5 b . 15 x 2 .a b 1 2 y z"
scale: str
valid and invalid like TESTSTRING, numbers are strings

[mpahl]

"."-Missings are always invalid
".a-.z" aren't recognized as invalid for string variables
negativ numbers are valid for cat variables but invalid for num variables

How this should be handled?

[hansendx]

Strings in the form of ^\.[a-z]{0,1}$ should be recognized as invalid.
Numbers might be a problem. Maybe we could add a parameter to customize invalid values for different studies in the future.