[R-sig-Geo] st_simplify outputs the input geometry with no simplification

[Michael Sumner]

It has changed it, there's now a mix of POLYGON and MULTIPOLYGON
geometries, but no change in the underlying coordinates. You have to use
the dTolerance argument:

nrow(st_coordinates(nc))
[1] 2529
nrow(st_coordinates(st_cast(nc_simplfy)))
[1] 2529
nrow(st_coordinates(st_cast(st_simplify(nc, dTolerance = 1000))))
[1] 1941

It still might change the geometry with dTolerance = 0 (the default), in
that case it will remove vertices that are collinear (unnecessarily dense
straight lines, reduce to two-vertex edges).  I only learnt that recently.

HTH



On Mon, Jul 22, 2019 at 8:15 PM Hugo Costa <hugoagcosta using gmail.com> wrote:

> Dear list,
>
> function st_simplify outputs exactly the same geometry as the input. This
> is an example:
>
> library(sf)
>
> nc = st_read(system.file("shape/nc.shp", package="sf"))
> nc <- nc %>% st_transform(3857)
> plot(st_geometry(nc))
>
> nc_simplfy<-st_simplify(nc)
> plot(st_geometry(nc_simplfy))
>
> However, I'm quite sure some days ago st_simpliffy was working as expected.
> Could it be something wrong in my machine? What am I missing?
>
> > sessionInfo()
> R version 3.5.3 (2019-03-11)
> Platform: x86_64-w64-mingw32/x64 (64-bit)
> Running under: Windows >= 8 x64 (build 9200)
>
> Matrix products: default
>
> locale:
> [1] LC_COLLATE=Portuguese_Portugal.1252  LC_CTYPE=Portuguese_Portugal.1252
>    LC_MONETARY=Portuguese_Portugal.1252 LC_NUMERIC=C
> [5] LC_TIME=Portuguese_Portugal.1252
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] sf_0.7-3
>
> loaded via a namespace (and not attached):
>  [1] compiler_3.5.3 magrittr_1.5   class_7.3-15   DBI_1.0.0
>  tools_3.5.3    units_0.6-2    Rcpp_1.0.1     grid_3.5.3     e1071_1.7-0.1
> [10] classInt_0.3-1
>
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>
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>


-- 
Michael Sumner
Software and Database Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner using gmail.com

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