[R] plot() and lines() multivariate problem
frederic.jean at univ-brest.fr
Fri Jan 10 17:45:03 CET 2003
I'm trying to solve the following problem since 2 days with no success.
Could someone help a newbie, please ?
I have a dependant variable which is diameter of shell, and two factors
which are level on the beach (3 levels 'B', 'E' and 'H') and a hydrodynamics
indice (3 levels 1, 2 and 3)
To study diameter variations according to these factors, I may use something
> mod <- lm(diameter ~ level * hydro)
When I want to look at the graphical results of such a model on a
scatterplot, I use
> plot(diameter ~ as.integer(hydro), col = as.integer(level))
and to draw the model lines :
> lines(as.integer(hydro)[lev=='B'], predict(mod)[lev=='B'], col = 1)
> lines(as.integer(hydro)[lev=='E'], predict(mod)[lev=='E'], col = 1)
> lines(as.integer(hydro)[lev=='H'], predict(mod)[lev=='H'], col = 1)
But sometimes, the lines are not drawn in the order of the levels of hydro but
as a *zigzag* and lines() commands seem to draw lines going from level 1
to level 3 and then back to level 2 of the x axis (hydro)
I hope this description is comprehensible. Could someone explain me how to
avoid this ?
Many thanks for giving me some of your time.
C'est curieux chez les marins, ce besoin de faire des phrases (M.A.)
Fred JEAN - UMR CNRS 6539 / LEMAR
Univ. Bretagne Occidentale - Inst. Univ. Européen de la Mer
Place Nicolas Copernic F-29280 PLOUZANE
Pho:+33 (0)2 98 49 86 38 // Fax:+33 (0)2 98 49 86 45
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