How to set up an ITS object, just the basics?

(Post manually approved; Taher you may want to subscribe to the list with
this address --Dirk)

Greetings!

Apologize for bringing up a really simple question, unfortunately I
cannot make sense of the help file for ITS.

I have a dataframe dfNAV which consists of a POSIXct date value %d/%m/%Y
and two values, some of which are NA's.

I want to set up an ITS object so that I can use locf().

Can someone please explain the syntax for setting it up? For example:

dfNAV.its <- its(as.matrix(dfNAV), format = '%d-%m-%Y')

Is it not working because I already have a date value, should I convert
it to a string before trying to make it an ITS?

It is really all there in the docs. The example section of help(its) has

   mat <- structure(1:6,dim=c(2,3),dimnames=list(c("2003-01-01","2003-01-04"),letters[1:3]))
   
which creates a matrix. Try class(mat), and then try  class(its(mat)).
Similarly 

   times <- as.POSIXct(strptime(c("1999-12-31 01:00:00","2000-01-01 02:00:00"),format="%Y-%m-%d %X"))

creates a POSIXct object which you can then use as the second argument to
its() -- try class(times) and class(its(mat,times)).

So in a nutshell, you can create its objects either way.  I tend to fill the
data and time components as two components, so 

   myIts <- its(myData, myDatesAsPosix) 
   
would be my choice.

Hope this helps, Dirk

Those are my principles, and if you don't like them... well, I have others.
                                                -- Groucho Marx