[R] confused with indexing
Jim Holtman
jholtman at gmail.com
Tue May 22 11:36:34 CEST 2012
use is.null for the test
if (is.null(indexSkipped))
Sent from my iPad
On May 22, 2012, at 2:10, Alaios <alaios at yahoo.com> wrote:
> Dear all,
> I have a code that looks like the following (I am sorry that this is not a reproducible example)
>
>
> indexSkipped<-NULL
>
>
>
> ....code Skipped that might alter indexSkipped
>
>
> if (length(indexSkipped)==0)
> spatial_structure<-spatial_structures_from_measurements(DataList[[i]]$Lon,DataList[[i]]$Lat,meanVector)
> else
> spatial_structure<-spatial_structures_from_measurements(DataList[[i]]$Lon[-indexSkipped],DataList[[i]]$Lat[-indexSkipped],meanVector) #
>
>
>
> What I am doing here is that I am processing files. Every files has a measurement table and Longtitude and Latitude fields. If one file is marked as invalid I keep a number of of the skipped index so to remove the element of the Longtitude and Latitide vectors.
>
> 1) That works correct, I was just wondering if it would be possible to remove some how the given if statement and initialize the indexSkipped in such a way so
>
> the DataList[[i]]$Lon[-indexSkipped],DataList[[i]]$Lat[-indexSkipped] do nothing, aka remove no element, in case the indexSkipped remains unchanged (in its initial value).
>
> 2) When u define a variable as empty, I usually use NULL, how I can check afterwords if that holds or not. If I use the
>
> (indexSkipped==NULL)
> logical(0)
>
> this does not return true or false. How I can do that check?
>
>
> Iwould like to thank you in advance for your help
>
> B.R
> Alex
> [[alternative HTML version deleted]]
>
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