Hi,

This is my first post in this page althougt i've been using R for several
months (by the way english is not my native language so sorry about the
grammar).

I have a problem with a xyplot on lattice, it's supossed to print different
lines for each river (Rio) conditioned by a chemical parameter (Var) and the
state at which it's located (Dpto) against the year the sample were taken
(Año)...actually it's doing quite right but the thing is that certarin lines
tendo to go first to a distant value and back to the supossed next value in
the series, e.g. the line goes from the value of 2002 to the value of 2004
and then back to the value of 2003 when it's supossed to go 2002 then 2003
then 2004!!

here is the code and the structure of the DB i'm using..

>car<-read.csv2("Historicos.csv")
>str(car)
'data.frame':   1818 obs. of  6 variables:
 $ Dpto  : Factor w/ 11 levels "ANTIOQUIA","ATLÁNTICO",..: 1 1 1 1 1 1 1 1 1
2 ...
 $ Rio   : Factor w/ 43 levels "Acandí","Anchicayá",..: 30 31 8 43 20 24 25
13 4 26 ...
 $ Var   : Factor w/ 13 levels "CAUDAL","CD",..: 1 1 1 1 1 1 1 1 1 1 ...
 $ Valor : num  13.1 3 3 2.9 2.8 ...
 $ Año   : int  2002 2002 2002 2002 2002 2002 2002 2002 2002 2002 ...
 $ Región: Factor w/ 2 levels "CARIBE","PACIFICO": 1 1 1 1 1 1 1 1 1 1 ...

#And the code for the plot

xyplot(Valor~Año|Dpto+Var,groups=Rio,data=car,
layout=c(4,3),scale=list(y=list(relation="free")),type="b",
skip=c(rep(F,11),T))

2- Actually i've another question concerning the same code, i also have to
plot the sum of each of the values for a given year (cause they're mass
loadings of pollutants), e.g. for each year with variable "DBO" and state
"MAGDALENA" i've to sum the values and show them as a single point in a
plot, i tried this but it's not working

xyplot(sum(Valor,na.rm=T)~Año|Dpto+Var,groups=Rio,data=na.omit(car),
layout=c(3,3),scale=list(y=list(relation="free")),type="p")

Could someone please tell me what i'm doing wrong and how to correct this,
please it's for a report i've to submit on Friday so please help me!!!
-- 
Marcos Antonio Carvajalino Fernández
Estudiante de Ingeniería Ambiental y Sanitaria
Universidad del Magdalena, Colombia

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