Tuesday, March 14, 2006

Re: Re: st: legend on graph help

Everyone's right here, in a sense.

-line- can be a separate command. It is, in that circumstance, an abbreviation for -twoway line-, which is in turn an abbreviation for -graph twoway line-.

. viewsource line.ado

shows the innards.

In essence, wired-in graph commands are all calls to -graph-, or wrappers for calls (to calls ( ... )) to -graph-.

But StataCorp were well aware that users probably don't want to type

. graph twoway line ...

whenever they want a line plot, hence the convenient abbreviations.

(FWIW, I always use the || notation. There are plenty enough parentheses already in a typical -graph- command.)

Nick n.j.cox@durham.ac.uk

"Svend Juul" <SJ@SOCI.AU.DK>

In a response to Scott C., Scott M. wrote, among other things:

2. It doesn't appear that the -legend(order())- (or the ytitle, yscale....) are attached to one of the -line- commands.

- and suggested:

twoway line mpg price if fore == 0 ,sort lc(blue) lp(dash) /// || line mpg price if fore == 1 , sort lc(black) /// legend(order(1 "white sex ratio" 2 "black sex ratio"))


Stata graph commands can be complex; I think it is helpful to keep the terminology straight:

-line- is not a command; it is a plot specification as part of a -twoway- graph command.


Personal view: I think the || notation is a lot less transparent than the () notation. So I would write the above command:

twoway /// (line mpg price if fore == 0 , sort lc(blue) lp(dash)) /// (line mpg price if fore == 1 , sort lc(black)) /// , /// legend(order(1 "white sex ratio" 2 "black sex ratio"))

Here we have a graph command (twoway) with two plot specifications (line); each plot specification has options (sort, etc.). The graph command also has an option: (legend()). ytitle() and yscale() would be graph options, too. I gave the comma separating the graph command body from the graph options a line of its own, just for visual clarity.

Stata often can be quite tolerant to deviations from the strict rules, as Scott M.'s example shows (it actually works), but I think that things are easier to understand when sticking to the rules.

* * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/


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