R help - Sep 2003 - readcsvIts() to create irregular time series

Dear,

Thanks for the previous tips about 'its' for importing the following
data.
5/10/1998,7
5/11/1998,5
5/12/1998,2
5/14/1998,1
5/15/1998,1
5/19/1998,1
5/20/1998,1

1. When using the following command;
test<-readcsvIts('Fires98.csv',informat=its.format("%m/%d/%Y"),header=FA
LSE)

the function reads in the data from the csv file as;
           V2
05/10/1998  7
05/11/1998  5

When testing if it's a its object
is.its(test) 
the result is FALSE.
When do you use informat or outformat? 
What goes wrong?

2. When reading in the data as a table;
m1 <- read.table('Fires98.csv',header=FALSE, sep=",",
dec=".")
          V1 V2
1  5/10/1998  7
2  5/11/1998  5
...
test2 <- its(m1,dates=as.POSIXct(x=strptime(dimnames(V1)[[1]]
format=its.format("%m/%d/%Y"))) )...Doesn't work! 

I have difficulties defining the first V1 column as its object.

Thanks in advance for helping me out,
Jan



________________________________________________________________________
__
Jan Verbesselt 
Research Associate 
Lab of Geomatics and Forest Engineering K.U. Leuven
Vital Decosterstraat 102. B-3000 Leuven Belgium 
Tel:+32-16-329750 
Fax: +32-16-329760
http://perswww.kuleuven.ac.be/~u0027178/VCard/mycard.php?name=janv
http://gloveg.kuleuven.ac.be/
________________________________________________________________________
__

Jan

The function readcsvIts reads a csv file into a matrix.  To convert 
the matrix into an 'its', apply the its function to the matrix.

So for your example

its.format("%m/%d/%Y")
test? <- its(readcsvIts(filename))
is.its(test)

"TRUE"

The its documentation for readcsvIts states incorrectly that an 'its'
object is returned, so your confusion is understandable.  I will correct 
this in the next release.

Giles
> -----Original Message-----
> From: Jan Verbesselt [mailto:Jan.Verbesselt at agr.kuleuven.ac.be]
> Sent: 01 September 2003 15:00
> To: r-help at stat.math.ethz.ch
> Subject: [R] readcsvIts() to create irregular time series
> 
> 
> Dear,
> 
> Thanks for the previous tips about 'its' for importing the
following
> data.
> 5/10/1998,7
> 5/11/1998,5
> 5/12/1998,2
> 5/14/1998,1
> 5/15/1998,1
> 5/19/1998,1
> 5/20/1998,1
> 
> 1. When using the following command;
>
test<-readcsvIts('Fires98.csv',informat=its.format("%m/%d/%Y")
> ,header=FA
> LSE)
> 
> the function reads in the data from the csv file as;
>            V2
> 05/10/1998  7
> 05/11/1998  5
> 
> When testing if it's a its object
> is.its(test) 
> the result is FALSE.
> When do you use informat or outformat? 
> What goes wrong?
> 
> 2. When reading in the data as a table;
> m1 <- read.table('Fires98.csv',header=FALSE, sep=",",
dec=".")
>           V1 V2
> 1  5/10/1998  7
> 2  5/11/1998  5
> ...
> test2 <- its(m1,dates=as.POSIXct(x=strptime(dimnames(V1)[[1]]
> format=its.format("%m/%d/%Y"))) )...Doesn't work! 
> 
> I have difficulties defining the first V1 column as its object.
> 
> Thanks in advance for helping me out,
> Jan
> 
> 
> 
> ______________________________________________________________
> __________
> __
> Jan Verbesselt 
> Research Associate 
> Lab of Geomatics and Forest Engineering K.U. Leuven
> Vital Decosterstraat 102. B-3000 Leuven Belgium 
> Tel:+32-16-329750 
> Fax: +32-16-329760
> http://perswww.kuleuven.ac.be/~u0027178/VCard/mycard.php?name=janv
> http://gloveg.kuleuven.ac.be/
> ______________________________________________________________
> __________
> __
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> 

********************************************************************** 
This is a commercial communication from Commerzbank AG.\ \ T...{{dropped}}

> BUT;
> 1. What can you do with informat and outformat? Is it the same as
> its.format() before the its function?
its.format() sets the text representation format for the times, and 
once set, it persists within that R session.  It is often convenient
to set this format just once in a session, since in many circumstances
multiple date formats serve only to distract and confuse.  The arguments
informat and outformat in readcsvIts override the value set in 
its.format().
> 
> 2. Can the its be plotted onto a ts? And is a correlation analysis in
> between the two objects possible?
> 
All regular time-series can be represented as irregular time-series -
they are a special case.  If you want to use both, I suggest you convert
your regular time-series to irregular.  You might for example use
seq.POSIXt(start,end,by="month") to set up a monthly series of POSIX
dates, and its(matrix,seq.POSIXt(start,end,by="month")) will then
provide
you with a reglar time-series reprented as an 'its'.

Having done this, you can plot multiple series, which may not have the 
same time-stamps, using for example:

xy <- unionIts(Fire,its(matrix,seq.POSIXt(start,end,by="month"))
plot(xy)
> 2. Can the its be plotted onto a ts? And is a correlation analysis in
> between the two objects possible?
A meaningful calculation of correlation normally requires the data to be 
aligned in time (I can't think of an exception to this).  So you need to 
ensure that you have at least some of the data 'aligned' to start off
with.
For example, if you have an 'its' x with daily data, and a 'its'
y with
monthly data, you could do the following:

cor(intersectIts(x,y))

It relies for success on at least some subset of the POSIX dates being 
equal, i.e. that the result of the intersect operation is not NULL.

Giles


********************************************************************** 
This is a commercial communication from Commerzbank AG.\ \ T...{{dropped}}