[R] build a SpatialLines object from a list

[Eric Berger]

Hi Ashraf,
In that case I think you may need to structure the code to first build the
list and only at the end supply that to the SpatialLines function,
something like

test.func <- function(x) {
    tt <- list()
    for ( i in ... )  {
       ...
       tt[[i]] <- (whatever)
    }
    return(SpatialLines(tt))
}

Eric


On Tue, Sep 26, 2017 at 12:36 PM, Ashraf Afana <asafaneh at yahoo.com> wrote:

> Hi Eric,
>
> Thanks for the help.But this will not solve the problem as it will
> generate a list and what I need is an object of class sp using SpatialLine
> function from sp package.So, I need to convert each matrix to coordinates
> and then to a line and then to a spatial line as figured in the code.
>
> My data structure is a list of 141 matrices.Each matrix represents
> coordinates of the river lines position.
>
> Ashraf, cheers
>
>
> On Monday, 25 September 2017, 16:56, Eric Berger <ericjberger at gmail.com>
> wrote:
>
>
> Hi Ashraf,
> It is not obvious to me what your structures are but one problem in your
> function is the assignment tt1 <- SpatialLines(list(tt[[i]])).
>
> This will set tt1 to just have one item.
>
> Consider the following
>
> test.func <- function(x) {
>     tt1 <- list()
>     for ( i in ... )  {
>        ...
>        tt1[[i]] <- SpatialLines(tt[[i]])
>     }
>     return(tt1)
> }
>
> HTH,
> Eric
>
>
> On Mon, Sep 25, 2017 at 3:40 PM, Ashraf Afana via R-help <
> r-help at r-project.org> wrote:
>
> Hi all,I'm trying to build a SpatialLines object from a list that contains
> 124 river segments. Each segment in the list contains the x,y coordinates.
> I'm using the following code to create the SpatialLines object, but it just
> retrieves one segment. Any suggestions?
>
> test.func = function(x){
>      for (i in 1:length(x)) {        tt[[i]] <- x[i]; tt[[i]]  =
> Line(tt[[i]]); tt[[i]]  = Lines(list(tt[[i]] ), 'i')        tt1 =
> SpatialLines(list(tt[[i]]))           }    return(tt1)  }
> Ashraf,
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>
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