sl.grid.mergepoints: Merge Nodes of an Unstructured Grid

In helgegoessling/spheRlab: Spherical Geometry, Analysis, and Plotting of Geoscientific Data on Arbitrary Grids

Merge Nodes of an Unstructured Grid

Description

Merge adjacent nodes of an unstructured grid. Neighbourhood information is updated accordingly and collapsing elements are removed.

Usage

sl.grid.mergepoints(grd, remove.points, merge.points, return.info = TRUE, auto.reduce = TRUE)

Arguments

grd	a spheRlab grid list as returned by sl.grid.readFESOM or sl.grid.curvilin2unstr. Must contain at least the following list-elements: elem (Ne x Me matrix; Melem=3 in case of a triangular grid), neighnodes (Nnn x Mnn matrix), and neighelems (Nne x Mne matrix). These matrices can contain NAs in the respective right-most columns. If auto.reduce=TRUE, additional list-elements in grd that are vectors are reduced as well whereby their length is used to detect whether they hold information valid for nodes or for elements.
remove.points	an integer vector specifying the nodes to be removed (merged into an adjacent node). Must have the same length as merge.points.
merge.points	an integer vector specifying the nodes into which the points in remove.points are to be merged. Must have the same length as remove.points.
return.info	a logical value specifying whether to return the indices of which nodes and elements of the original grid have been kept. Can be used e.g. to extract corresponding data values valid for the unmerged grid.
auto.reduce	a logical value specifying whether to reduce additional list-elements in grd that are vectors. If so, the vector length is used to detect whether the list-elements hold information valid for nodes or for elements.

Details

If auto.reduce=TRUE, additional list-elements in grd that are vectors are reduced as well whereby their length is used to detect whether they hold information valid for nodes or for elements.

Value

a grid list with the same (partly modified) elements as grd. If return.info=TRUE, an additional element merge.kept with sub-elements nodes and elems providing the indices of nodes and elements of the original grid that have been kept.

Author(s)

Helge Goessling

See Also

sl.grid.curvilin2unstr, sl.grid.reduce

Examples

# generate an example curvilinear grid
lon.0 = seq(-60,60,30)
lat.0 = seq(-30,30,20)
grd1 = sl.grid.curvilin2unstr(lon = lon.0, lat = lat.0)
grd1$coast = rep(FALSE,length(grd1$lon))
grd1$coast[c(1:5,10,15,20)] = TRUE

# merge four nodes into adjacent nodes
grd2 = sl.grid.mergepoints(grd1, remove.points = c(4,5,7,14), merge.points = c(9,10,6,15))

# initialize plot
pir = sl.plot.init(projection = "lonlat", lonlat.lonrange = c(-70,70), lonlat.latrange = c(-35,35), do.init.device = FALSE)

# plot original grid, including node and element numbers and coast symbols
sl.plot.elem(pir, lon = grd1$lon, lat = grd1$lat, elem = grd1$elem, col.border = "blue")
sl.plot.points(pir, pch = 1, lon = grd1$lon[grd1$coast], lat = grd1$lat[grd1$coast], col = "blue")
sl.plot.text(pir, labels = 1:length(grd1$lon), lon = grd1$lon-3, lat = grd1$lat, col = "blue")
for (i in 1:nrow(grd1$elem)) {
  sl.plot.text(pir, labels = i, lon = mean(grd1$lon[grd1$elem[i,]])-3, lat = mean(grd1$lat[grd1$elem[i,]]), col = "cyan")
}

# plot new grid, including node and element numbers and coast symbols
sl.plot.elem(pir, lon = grd2$lon, lat = grd2$lat, elem = grd2$elem, fill = FALSE, lty = 2, col.border = "red")
sl.plot.points(pir, pch = 4, lon = grd2$lon[grd2$coast], lat = grd2$lat[grd2$coast], col = "red")
sl.plot.text(pir, labels = 1:length(grd2$lon), lon = grd2$lon+3, lat = grd2$lat, col = "red")
for (i in 1:nrow(grd2$elem)) {
  sl.plot.text(pir, labels = i, lon = mean(grd2$lon[grd2$elem[i,]])+3, lat = mean(grd2$lat[grd2$elem[i,]]), col = "orange")
}

# finish plot
sl.plot.end(pir, do.close.device = FALSE)

helgegoessling/spheRlab documentation built on April 8, 2024, 8:34 a.m.