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help for ^defv^                                    [STB-40: dm50; STB-51: dm50.1]
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Define variables and record their definitions
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   ^defv^ [^by^ varlist^:^] [type] newvar [^:^ lblname] ^=^ exp [^if^ exp] [^in^ range]

   ^defv^ [^by^ varlist^:^] oldvar ^=^ exp [^if^ exp] [^in^ range] [^, nop^romote]

   ^defv^ oldvar ^?^

   ^defv^ ^?^
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Description
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^defv^ creates a new variable or changes the contents of an existing
variable, whichever is appropriate, and records the operation it
performed in a charac- teristic attached to the variable.  The first
syntax above is applicable in the case of a new variable, the second
and third apply to existing variables. Aside from the positioning of a
^by^ clause (i.e., following rather than preceding the command name),
the first syntax is identical to that of the @generate@ command, the
second to that of the @replace@ command.

^defv^ is a wrapper for the built-in commands ^generate^ and ^replace^
that makes it possible to define a variable and record its definition
by repeatedly using a single command (^defv^), regardless of whether
the variable exists at the outset.  The definition is recorded in a
series of ^characteristics^ associated with the variable (one
characteristic for each use of ^defv^); the third syntax above dis-
plays those characteristics, in the order recorded. The fourth syntax
serves as a reminder of the first three.

^defv^ may be freely used in place of ^generate^ and ^replace^, with
two alterations: (1) a ^by^ clause follows the name ^defv^, whereas it
precedes the names ^generate^ and ^replace^; (2) the name of the
variable being defined cannot be abbreviated.
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Options
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There are no options other than those associated with ^generate^ and
    ^replace^.
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However, it is possible to alter the style in which ^defv^ records
    definitions.  By default, ^defv^ uses the same naming scheme as the
    command @notes@, so that re- corded definitions will appear to have
    been created by ^notes^.  Definitions from ^defv^ and notes from
    ^notes^ may be freely intermingled.  If this is undesirable,
    definitions can be rendered distinct from notes by altering a comment
    line near the top of the file defv.ado.
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Examples
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 . ^defv age2 = age*age^
 . ^defv income=. if income<=0^
 . ^defv byte biginc = income>100000 & income~=.^
 . ^defv xlag = x[_n-1] in 2/l^
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 . ^replace sw = 1 if region=="SW"^     (OK)
 . ^defv sw = 1 if region=="SW"^        (Also OK)
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 . ^sort loc^
 . ^defv by loc: avgx = sum(x)/sum(x~=.)^
 . ^defv by loc: avgx = avgx[_N]^
 . ^defv avgx ?^
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Author
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   John R. Gleason, Syracuse University, Syracuse NY, USA
   (loesljrg@@accucom.net)    [This is Version 1.1.3 (06Mar1999).]
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Also see
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 Manual:   ^[U] 19 Data^
           ^[U] 19.8 Characteristics^
           ^[U] 20 Functions and expressions^
           ^[R] generate^
           ^[R] notes^
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 On-line: help for @char@, @datatypes@, @exp@, @functions@,
          @generate@, @notes@, @operators@