R help - Sep 2017 - build a SpatialLines object from a list

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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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,
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
	[[alternative HTML version deleted]]

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,
? ? ? ? [[alternative HTML version deleted]]

______________________________ ________________
R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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.



   
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