[R] [FORGED] find numbers that fall in a region or the next available.

[David L Carlson]

Assuming your map area can be described as a closed polygon, these functions would tell you which points lie within the boundaries of the polygon.

David C

From: Alaios [mailto:alaios at yahoo.com] 
Sent: Thursday, February 4, 2016 1:34 AM
To: David L Carlson; r-help at r-project.org
Subject: Re: [R] [FORGED] find numbers that fall in a region or the next available.

That is a great tip thanks.
That would indeed bring me points that are the closes to my area.. but if I am not wront that returns points that are part of a circle surface. It might be that I get a point that is just 50 meters outside of my map area. Is not that true? I would need after I find closest point to confirm which ones fall inside my map region.

Alex

On Wednesday, February 3, 2016 8:36 PM, David L Carlson <dcarlson at tamu.edu> wrote:

Look at the point.in.polygon() and over() functions in package sp.

-------------------------------------
David L Carlson
Department of Anthropology
Texas A&M University
College Station, TX 77840-4352

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Alaios via R-help
Sent: Wednesday, February 3, 2016 2:42 AM
To: Rolf Turner; R-help Mailing List
Subject: Re: [R] [FORGED] find numbers that fall in a region or the next available.

Thanks. I am using distm of the geoshere package.I still wonder if there is a package that can tell me if a gps coordinate or not fal

ls inside my area that is defined as:
bbox <- c(min(PlotPoints[, 1])-0.001, min(PlotPoints[, 2])-0.001, max(PlotPoints[, 1])+0.001, max(PlotPoints[, 2])+0.001)

PlotPoints are gps coordinates.
That would make it sure that I have no mistakes in my code.
Any ideas?Alex 

    On Tuesday, February 2, 2016 11:33 PM, Rolf Turner <r.turner at auckland.ac.nz> wrote:


On 03/02/16 11:04, Alaios via R-help wrote:
> Dear all,I have GPS coordinates (one vector for longitude and one for
> latitude: GPSLong and GPSLat) of small are that is around 300meters X
> 300 meters (location falls inside UK).At the same time I have two
> more vectors (Longitude and Latitude) that include position of food
> stores again the UK I would like to find within my 300x300 square
> area which as the food stores that fall inside.I thought to try to
> find which of the Longitude of the food stores fall inside my area. I
> tried something the below
>
> Longitude[Longitude>(min(GPSLong)-0.001)&&Longitude<(max(GPSLong)+0.001)]
> but this returned me zero results.The next option would be the code
> to return me at least the place that falls outside but still is close
> to that region.'Do you have any idea how to do that and not fall back
> in the time consuming look at each element iteration?
> I would like to thank you for your reply


You could make use of the distfun() function from the spatstat package. 
  Represent your "small area" as an object of class "owin".  The 
longitude and latitude coordinates will be treated as if they were 
Euclidean coordinates, but over distances of the order of 300 metres 
this should not matter much.  You could of course convert your long and 
lat coordinates to metres, using some appropriate projection, which 
might make more sense in your context.

cheers,

Rolf Turner

-- 
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276


  
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