Thank you David. 
The plot() you sugested worked nicely.
 
You and Weyland both think ts class objects are difficult to use. I had not considered doing differently, but I have just gotten many tutorials on package zoo and how to use it in econometrics. Looks promising, will read everything now.
But let me ask first, I am going to do some exercises using vars package, and I wanted to replicate on my own database the following script (below) that I have managed to put together using the data Canada (available in R):
So I compared the structure of "Canada" and I concluded it was a "ts" object, and that's why I decided to create my own data the same way. Is this necessary or am I taking an irrelevant precaution? 
 
> str(Canada)
 mts [1:84, 1:4] 930 930 930 931 933 ...
 - attr(*, "dimnames")=List of 2
  ..$ : NULL
  ..$ : chr [1:4] "e" "prod" "rw" "U"
 - attr(*, "tsp")= num [1:3] 1980 2001 4
 - attr(*, "class")= chr [1:2] "mts" "ts"

> str(dados2) #my database on public dept
 mts [1:210, 1:44] 83 65 136 13 154 118 100 30 205 188 ...
 - attr(*, "dimnames")=List of 2
  ..$ : NULL
  ..$ : chr [1:44] "data" "igpm" "ipca" "iigpdi" ...
 - attr(*, "tsp")= num [1:3] 1994 2011 12
 - attr(*, "class")= chr [1:2] "mts" "ts"

 
 
> data("Canada")
> plot(Canada,nc=2,xlab="")
> VARselect(Canada,lag.max=8,type="both")
> Canada<-Canada[,c("prod","e","U","rw")]
> pict<-VAR(Canada,p=1,type="both")
> summary(pict,equation="e")
> varcov[1:4,1:4]=summary(pict)$covres[1:4,1:4]  #getting the covar . I had problem with this comand, so i used instead as below:
>getVarCov=summary(pict)$covres[1:4,1:4]
> c=chol(varcov) #Choleski
> u=rnorm(4)     #vetcor with 4 random variables N(0,1)
> P=c%*%u        #matricial multiplication choleski%*%rnorm
> xteste=matrix(1:6,nrow=6,ncol=1) # generates a test vector for X
### Start - coefficients of each equation ###
> coef_e=pict$varresult$e$coefficients
> coef_rw=pict$varresult$rw$coefficients
> coef_U=pict$varresult$U$coefficients
> coef_prod=pict$varresult$prod$coefficients
> coef=rbind(coef_prod,coef_e,coef_U,coef_rw)
### End - generates coef matrix with the coefficients of each equation
> coef%*%xx+P  #simulates vector Yt+1, conditioned to shocks in vector X and shocks already ajusted between the variables by the covar
 
 


________________________________
De: David Winsemius <dwinsemius@comcast.net>

Cc: "r-help@r-project.org" <r-help@r-project.org>
Enviadas: Segunda-feira, 17 de Outubro de 2011 22:09
Assunto: Re: [R] Beginner's question about plotting variables in a time series object with the date on the x axis


On Oct 17, 2011, at 5:23 PM, Iara Faria wrote:

> Dear R helpers,
> 
> I am a beginner at R so please be gentle :)
> I have already read manuals and FAQs, with no help.
> I have a monthly time series data on public debt with 40 variables, it starts on January 1994 and ends on June 2011.

I agree with Weyland. Figuring out how to use class `ts` objects in R is difficult. If it were easy I don't think Zeileis would have invented `zoo`.

> I am loading the data into R using read.csv and the data looks ok when I do edit(dados):
>> dados<-read.csv("dadosR3.csv", header=T)
> then I tried making it into a time series object, using:
>> dados2<-ts(dados, start = c(1994,1), frequency=12)

(See below for what that did.)

> 
> Now when I try plotting any of the variables, for example divliq.pib (net debt), the date doesn't appear on the x axis. How can I do this?
> I use
>> plot.ts(divliq.pib)


Try:

plot(time(dados2), dados[, "divliq.pib"] , xy.labels=FALSE))

> 
> also the function names() doesn't work, which would be important since I have so many variables.
>> names(dados2)

Read the help page again(?). "A data frame will be coerced to a numeric matrix via data.matrix."

The names function only works for lists and name vectors. Try colnames()

> NULL
> 
> I am using R.2.13.1
> 
> Thank you very much.
>     [[alternative HTML version deleted]]
> 
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> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT
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