st: gr tw (scatter if) (scatter if), by()

[David Airey <david.airey@vanderbilt.edu>]

.scatter lens_average eye_nolens if parity <= 9, by(parity)

gives a 3 x 3 graph of nine plots (parity 1, 2 to 9)

.tw lfit lens_a eye_n if parity <= 9, by(parity)

gives a 3 x 3 graph of nine plot

.tw (scatter lens_average eye_nolens if parity <= 9) ///
	(lfit lens_average eye_nolens if parity <= 9), by(parity)

gives the message:

. tw (scatter lens_average eye_nolens if parity <= 9) ///
>         (lfit lens_average eye_nolens if parity <= 9), by(parity)
no observations

but completes a graph (3 x 4) leaving three holes in positions 10-12.

Is this behavior intended?

Given the first two graphs, I would have thought the by() option would 
travel through the overlay of the plots properly. It doesn't, at least 
not the way I intended.

Maybe I should have simply done,

preserve
drop if parity > 9
tw (scatter lens_average eye_nolens) ///
   (lfit lens_average eye_nolens), by(parity)
restore


-Dave

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