[R-sig-Geo] Building a vector of random sf st_points

[Edzer Pebesma]

On 21/12/16 17:25, Pierre Racine wrote:
> Hi,

Hi Pierre!

> 
> Very new to spatial R. I'm trying to find the best way to build a sf dataframe of random points inside an extent. I built a matrix of random coordinates and now I try to convert this matrix to a vector of st_point.
> 
> I was expecting that something like:
> 
> PTS <- matrix(seq(1,6), 3, 2)

> st_sfc(lapply(seq_len(nrow(PTS)), function(i) st_point(PTS[i,])))
Geometry set for 3 features
geometry type:  POINT
dimension:      XY
bbox:           xmin: 1 ymin: 4 xmax: 3 ymax: 6
epsg (SRID):    NA
proj4string:    NA
POINT(1 4)
POINT(2 5)
POINT(3 6)


> ptsdf <- apply(PTS, 1, st_point)
> 
> would work but it doesn't. Why?

apply wants to to mold the output into a matrix; it can, and so it does.
We want a list of POINT objects, so need to use lapply.

-- 
Edzer Pebesma
Institute for Geoinformatics  (ifgi),  University of Münster
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences:   http://elsevier.com/locate/cageo/

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