# RE: st: Graphing some Isobars..

 From "Nassar" To Subject RE: st: Graphing some Isobars.. Date Fri, 24 Sep 2004 11:03:01 +0200

```Nick & Stas, thanks for your reply..

Maple, Gauss, R use "contour plot" terminology..
It took some time to get this graph out in R (never use it before)

Thanks for the detailed terminology
Naji

-----Message d'origine-----
De : owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu]De la part de Nick Cox
Envoyé : jeudi 23 septembre 2004 15:54
À : statalist@hsphsun2.harvard.edu
Objet : RE: st: Graphing some Isobars..

I agree with Stas. At present, you
need to go outside Stata for this.

As a geographer and word-nut, I can
comment on the terminology here.
None of what follows helps solve the
problem, or indeed any other problem,
so you can bail out here.

Isobars are strictly lines of equal (atmospheric)
pressure on a map. Contours were originally
lines of equal (surface) altitude, but
clearly are understood much more broadly.
Some geographers have used "isarithm"
or "isopleth" as general terms; the
latter is perhaps more widespread, and
can be contrasted with "choropleth"
for maps in which values are shaded by
areas (e.g. states or counties).
Tukey hit the nail on the head in calling
the last "patch maps". A disadvantage
of "choropleth" is that many people's memories
of studying photosynthesis when young makes
them write "chloropleth".

In days when some scholars used to show
off what Greek they know, or had found
in a dictionary, almost every kind of
line showing constant values was given
a distinct name: some have flourished
in limited fields, e.g. isotherm (temperature),
isohyet (rainfall), isobath (depth).
Some failed to get off the ground, e.g.
isonoet (lines of equal IQ), found I believe
only in one study of IQ patterns in Tasmania.

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

Stas Kolenikov

> Another name I know this under is the countour plot. There are some
> routines that go back into prehistoric period of Stata graphics (i.e.,
> before 8), but they are way too basic. This is a long awaited feature
> for me, and so far S-Plus/R is much better in graphs of this kind.

Nassar

> > I have three variables, X Y & Z (all 3 continuous)... How
> can I graph
> > 'isobars', ie linkings (x,y) so that Z(x,y) is constant

*
*   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/

```

<<attachment: winmail.dat>>