Thanx Ashton,

Experimenting on a starting point from Google maps
 p<-c(41.32217,19.802721)

> simCoords(p,500)[1] 125.7413 512.6246.

I suppose these are in radians and need to be converted?

using

> distances <- c(0.00000000,  0.02725136,  1.07634471, 1.15963225,+                1.71421571,  2.54945626, 4.29135102,  4.53532958,  4.58512710,  4.86466833,+                5.24266630,  5.63505465)> > exampleCoords <- lapply(distances, simCoords, origin=c(41.32217,19.802721))> plot(41.32217,19.802721, xlim=c(-10,10), ylim=c(-10,10), pch=2, col='blue', cex=2,+      main='Points near a bus stop')> for (p in 1:length(exampleCoords)) {+     points(exampleCoords[p][[1]][1],exampleCoords[p][[1]][2])+ }

I still dont get any results.

What I am doing wrong?

Please help me understand.

Regards




On Thu, Apr 18, 2013 at 8:28 PM, Ashton Shortridge <ashton@msu.edu> wrote:

> Dear Endri,
>
> do you simply wish to simulate coordinates for these locations? Because,
> assuming you are working on a planar system and those distances are
> euclidean,
> each of those distances is a radius for an infinite number of locations on
> a
> circle around your bus stop.
>
> Code like this might then do what you want:
>
> simCoords <- function(origin, dist) {
>     # 'origin' is a 2-element vector (x,y) of the starting coordinate
>     # 'dist' is the distance of the offset from this origin to simulate
>
>     # simulate an angle in radians
>     alpha <- runif(1,-pi,pi)
>
>     # Calculate x and y offsets
>     yoff <- dist * sin(alpha)
>     xoff <- dist * cos(alpha)
>
>     # Add offsets to origin, return a vector coordinate
>     return (c(origin[1] + xoff, origin[2] + yoff))
> }
>
> # Simple function test
> simCoords(c(0,0), 10)
>
> # Graphical test of the function
> plot(0,0, xlim=c(-15,15), ylim=c(-15,15), main='This had better look like a
> circle!')
> for (i in 1:1000) {
>     pt <- simCoords(c(0,0), 10)
>     points(pt[1], pt[2])
> }
>
> # Test using your distances
> distances <- c(0.00000000,  0.02725136,  1.07634471, 1.15963225,
> 1.71421571,  2.54945626, 4.29135102,  4.53532958,  4.58512710,  4.86466833,
> 5.24266630,  5.63505465)
>
> exampleCoords <- lapply(distances, simCoords, origin=c(0,0))
> plot(0,0, xlim=c(-10,10), ylim=c(-10,10), pch=2, col='blue', cex=2,
> main='Points near a bus stop')
> for (p in 1:length(exampleCoords)) {
>     points(exampleCoords[p][[1]][1],exampleCoords[p][[1]][2])
> }
>
> # A final test: plotting many, many simulations should look like a map of
> nested circles
> plot(0,0, xlim=c(-10,10), ylim=c(-10,10), pch=2, col='blue', cex=2,
> main='Points near a bus stop, nsim=200\nThis should look like a bunch of
> nested circles!')
> for (i in 1:200) {
>     exampleCoords <- lapply(distances, simCoords, origin=c(0,0))
>     for (p in 1:length(exampleCoords)) {
>         points(exampleCoords[p][[1]][1],exampleCoords[p][[1]][2], cex=0.4)
>     }
> }
>
>
> Hope this helps,
>
> Ashton
>
> On 04/18/13, Endri Raco, wrote:
> > Hi group,
> > I am stacked in a problem like this.
> > I have a bus stop with known coordinates.
> > I generate in R language distances from this bus stop. Values of these
> > distances are like below
> > (in km)
> >
> >
> > 0.00000000  0.02725136  1.07634471  1.15963225  1.71421571  2.54945626
> > 4.29135102  4.53532958  4.58512710  4.86466833  5.24266630  5.63505465
> >
> > I need to convert this distances in coordinates in order to reflect
> > points in map which are these distances far from starting bus stop.
> >
> >
> >
> > Any ideas about this?
> >
> > Please help
> >
> > Regards
> >
> >       [[alternative HTML version deleted]]
> >
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo@r-project.org
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>
>
> -----
> Ashton Shortridge
> Associate Professor                     ashton@msu.edu
> Dept of Geography                       http://www.msu.edu/~ashton
> 235 Geography Building          ph (517) 432-3561
> Michigan State University               fx (517) 432-1671
>



-- 
MSc. Endri Raço
_________________________________________________
Polytechnic University of Tirana
Faculty of Mathematical Engineering and Physics Engineering
Department of Mathematical Engineering
Address:  Sheshi Nene Tereza, Nr. 4, Tirana - ALBANIA
Mobile: ++ 355 682061988

	[[alternative HTML version deleted]]

