st: 'twoway' syntax subtlety

[George Hoffman <ghoffman@mcw.edu>]

I'm trying to overlay two (or more) kdensity plots.

kdensity accepts the 'norm' option
twoway kdensity does not - see log below

I thought twoway calls kdensity - but I must have a misunderstanding of
stata 10 graphics....

An explanation of principle would be most appreciated.
Thank you,
George Hoffman



This my Stata 10 log:

. two (kdensity rso2c if vmi85==0) (kdensity rso2c if vmi85==1)

. two (kdensity rso2c if vmi85==0,norm) (kdensity rso2c if vmi85==1,norm)
option norm not allowed
r(198);

. kdensity rso2c if vmi85==0,norm

. two kdensity rso2c if vmi85==0,norm
option norm not allowed
r(198);


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