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Re: st: Plotting several polynomials on the same graph


From   Miranda Kim <mk@mrc.soton.ac.uk>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Plotting several polynomials on the same graph
Date   Fri, 17 Jul 2009 16:25:11 +0100

Thanks a lot for this!
I wondered if there is any way of adding functions onto the same graph using a separate command (on a separate line), so as to be able to loop over these and superimpose several (i.e. instead of using the '||' in the 'twoway' command)
Many thanks,
Miranda

Maarten buis wrote:
--- On Fri, 17/7/09, Miranda Kim <mk@mrc.soton.ac.uk> wrote:
I have three variables that hold coefficients for
polynomials (such that each row contains three coefficients
for a simple polynomial y=a+bx+cx^2). I want to draw all
polynomials (10 rows) on the same graph.

Then (if possible) I have three variables that hold three
points that lie on the graph (each row contains three points
that lie on the polynomial that is defined by the
coefficients on that row), I’d like to plot these too (on
the same graph).

Does this solve your first question?

*-------------- begin example -------------------
input a b c
1 2 3
2 3 4
end

twoway function y = a[1] + b[1]*x + c[1]*x^2, ///
       range(-3 3) || ///
function y = a[2] + b[2]*x + c[2]*x^2, /// range(-3 3) *---------------- end example -------------------

I don't understand the data structure involved in your second question: a point on that curve should be defined by two values: and x coordinate and a y coordinate. If you have those you can use
-scatter- as an overlay plot within the example
I gave above. You could also consider the -xline()- or -yline()- options.

Hope this helps,
Maarten

-----------------------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://home.fsw.vu.nl/m.buis/
-----------------------------------------


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