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


From   Gary Longton <glongton@fhcrc.org>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Accessing and changing -graph- options in a program
Date   Mon, 23 Feb 2009 14:12:32 -0800

Bert Jung wrote:

I am writing a program that customizes a graph.  I want the common
-graph- options to be available in my program, but override some of
them with settings that I define in the program itself.  I am looking
for a way to access and change some of the allowed -graph- options
inside my program.

In the below example, if the user does not specify the option - ,
xtitle() - the program assigns a default value.  I can implement this
by specifying my own option xtitle() in the syntax and then
substituting the content of the `xtitle' macro.  But there must be a
better way to access all those options than listing them in the
syntax?

The easiest approach to passing user-specified graph options from your program to an included graph command is to use the wild card [*] option. Any and all user specified options that are not otherwise explicitly included in your syntax command are consequently placed in the `options' macro. This macro can then be included in (usually at the end of) your graph/scatter command. Whether you additionally include specific options in your ado syntax command in order to test for a user override or not will depend on the type of graph option.

  (see -help repeated options- or [G] concept: repeated options)

If it is a *rightmost*, or *merged-explicit* option, then you don't need to worry about testing for the presence of the option in your program syntax. By including the `options' macro at the end of the scatter/graph command, the first instance of the option, if it exists, will be ignored (or merged if there are otherwise unspecified suboptions included in the first instance of the option).

For example, xtitle() is merged-explicit. Since you want a) to provide your own default title, and b) allow for a user overide of your default, your example could be more simply coded as follows:

************************
** Example for xtitle

sysuse auto, clear

cap program drop mygraph
program mygraph
    syntax varlist(min=2 max=2), [ * ]
    scatter `varlist', xtitle("default title") `options'
end

* Graph with default xtitle
mygraph  weight mpg

* Graph with user-specified xtitle
mygraph  weight mpg, xtitle("user specified xtitle")

************************

If you wish to include a program defined default for an *unique* option (eg. saving()) , you will probably want to explicitly include the option in you syntax as you did in your example, so as to include only one instance of the option in your -graph- call. Unique options specified more than once in a graph command will return an error.


- Gary
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