[R] Is there any way to know when a field is blank

[Gabor Grothendieck]

If the problem is how to remove rows with NAs then

   fxdata <- na.omit(fxdata)

will do it and

   if (length(fxdata) > 0) ...

will check the length.

On 11/21/06, Chuck Cleland <ccleland at optonline.net> wrote:
> Leeds, Mark (IED) wrote:
> > I have many text files in the format below and in certain rare instances
> > such as below there can be nothing in one of the fields so
> > a double comma is written but I won't know this because I am reading in
> > many,many files sequentially.
> >
> > # TEXT FILE
> >
> > 2004-02-10 00:01:31.00000,,105.60000000
> > 2004-02-10 00:01:32.00001,,105.60000000
> > 2004-02-10 00:01:45.00000,,105.60000000
> > 2004-02-10 00:01:49.00000,,105.61000000
> > 2004-02-10 00:02:08.00000,,105.60000000
> > 2004-02-10 00:02:15.00000,,105.60000000
> > 2004-02-10 00:02:23.00000,,105.60000000
> > 2004-02-10 00:02:41.00000,,105.60000000
> > 2004-02-10 00:03:09.00000,,105.59000000
> > 2004-02-10 00:03:16.00000,,105.60000000
> > 2004-02-10 00:03:19.00000,,105.59000000
> > 2004-02-10 00:03:25.00000,,105.60000000
> > 2004-02-10 00:03:39.00000,,105.59000000
> > 2004-02-10 00:03:52.00000,,105.60000000
> > 2004-02-10 00:03:54.00000,,105.60000000
> >
> > # LINES OF CODE
> >
> > fxdata<-read.zoo(file=fxfile,FUN=as.POSIXct,sep=",",col.names=c("date","
> > bid","ask"))
> > fxdata<-fxdata[( fxdata[,"bid"] > 0.0 ) & ( fxdata[,"ask"]  > 0.0 ),]
> > aggfxdata<-as.zoo(aggregatebyminutes(zooobj=fxdata,aggtimeframe=aggtimef
> > rame))
> >
> > #=======================================================================
> > ====================
> >
> > Even with the double comma being there, the fxdata<-read.zoo line and
> > the fxdata<-fxdata line still work but then on
> > the aggfxdata<-as.zoo line , I get the error :
> >
> > "Error in rep.int(seq(1:d[i]), prod(d[seq(length = i - 1)]) * rep.int(1,
> > :
> >         invalid number of copies in rep()"
> >
> > This error is reasonable because the routines, aggregatebyminutes,
> > probably has a problem with nothing
> > being in the bid field. My question is if there is some way tha I can
> > know that nothing
> > is in the bid field so that I can skip this file altogether and go onto
> > the next one ?
> > I'm not showing the details of the function because I'm not interested
> > in the error. I am only interested in knowing
> > that the "bid" field does not exist.
> >
> > I ask only because I am unsure how often this double comma/missing field
> > scenario can happen so it would
> > be better to automate the skipping of the file.
>
>  You could avoid the as.zoo() part when dim(fxdata)[1] is equal to zero
> with something like this:
>
> library(zoo)
>
> fxdata <- read.zoo(file="fxfile", FUN=as.POSIXct, sep=",",
>                   col.names=c("date","bid","ask"))
>
> fxdata <- fxdata[(fxdata[,"bid"] > 0.0) &
>                 (fxdata[,"ask"] > 0.0),]
>
> if(dim(fxdata)[1] == 0) cat("\n All missing! \n") else{
> aggfxdata <- as.zoo(aggregatebyminutes(zooobj=fxdata,
>                    aggtimeframe=aggtimeframe))
> }
>
>  I'm not sure how to know without reading the file whether you have
> this problem, but once you have read it and know that dim(fxdata)[1] ==
> 0, you can remove fxdata with rm().
>
> > Thanks.
> > --------------------------------------------------------
> >
> > This is not an offer (or solicitation of an offer) to buy/se...{{dropped}}
> >
> > ______________________________________________
> > R-help at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
> --
> Chuck Cleland, Ph.D.
> NDRI, Inc.
> 71 West 23rd Street, 8th floor
> New York, NY 10010
> tel: (212) 845-4495 (Tu, Th)
> tel: (732) 512-0171 (M, W, F)
> fax: (917) 438-0894
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>