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Re: st: Accessing and changing -graph- options in a program

From   Gary Longton <>
Subject   Re: st: Accessing and changing -graph- options in a program
Date   Mon, 23 Feb 2009 17:46:11 -0800

Bert Jung wrote:
Many thanks Gary.  Is there any way to restrict the `options' macro to
contain only elements allowed by -graph-?  My worry is that the
wildcard [ * ] would collect any user input and could generate an
error message at the end of the program.


Not that I am aware of, at least not at the level of the syntax command.

But the only user input that will be collected in `options' is that not allowed by your syntax statement otherwise. If user input isn't explicitly allowed by the -syntax- command or doesn't consist of valid twoway options allowed by the internal graph command, then it seems to follow that your program *should* return an error.

So the question isn't whether the disallowed user input will return an error. It will and should return an error whether [*] is included or not. Including [*], in addition to allowing the inclusion of -twoway options-, only delays the disallowed syntax error until the -twoway- command is called. The error returned by the internal graph command resulting from disallowed arguments passed via `options' will be a meaningful one - it should identify the first disallowed argument in the list - and should be similar to that which would otherwise be returned by the initial syntax command in -mygraph- if [*] were not included.

If writing the program for other users, you are likely to include a help file which will specify the allowed options for -mygraph-, including an entry indicating that generic twoway_options are allowed. Eg. The help file line from -histogram-, an official Stata ado also which uses [*] to capture and pass along graph command options reads:

. . .
  . . .
  twoway_options       any options documented in [G] twoway_options
. . .

So users will know that not just "any input" is allowed, but that any of the standard -twoway options- are permitted.

- Gary

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