Three-dimensional spatial plots

sdplot31, sdplot32 and sdplot33 draw spatial objects in a three-dimensional coordinate system rather than the flat one plot() uses. That system comes from psetup3, so the ranges of all three axes and the direction the plot is viewed from are set up once with tda_sd_ps3(), the 3-D counterpart of tda_ps – tda_sd_pl3_points(), tda_sd_pl3_lines() and tda_sd_pl3_polygons() then add drawing commands to it the way tda_pl_lines and its siblings add to a tda_ps session, and plot() draws the result. tda_pl_text3 and tda_pl_points3 (TDA's 3-D-aware commands, not tied to a spatial file) work on a tda_sd_ps3 session too, which is how a title or an extra marker gets added – TDA's ordinary plabel() (tda_pl_labels) is 2-D only and refuses outright with “current coordinate system is 3-dimensional” if tried here. tda_pl_lines3, by contrast, does not work on a tda_sd_ps3 session: it folds its coordinates into a regular nvar variable, which needs an ordinary nvar declaration that a spatial session, declared with sdnvar instead, does not have – “Syntax error or undefined variables”. Use tda_pl_points3 instead, which takes literal coordinates and needs no such declaration.

Usage

tda_sd_ps3(
  s,
  xlim = NULL,
  ylim = NULL,
  zlim,
  view = c(30, 30),
  width = 100,
  ...
)

tda_sd_pl3(p, cmd, ..., zvar = NULL)

tda_sd_pl3_points(p, symbol = 1, size = NULL, zvar = NULL, zval = NULL, ...)

tda_sd_pl3_lines(p, symbol = NULL, size = NULL, zvar = NULL, zval = NULL, ...)

tda_sd_pl3_polygons(
  p,
  symbol = NULL,
  size = NULL,
  zvar = NULL,
  zval = NULL,
  ...
)

tda_sd_plot3(
  s,
  z,
  xlim = NULL,
  ylim = NULL,
  view = c(30, 30),
  width = 100,
  newpage = TRUE,
  symbol = 1,
  size = NULL,
  zvar = NULL,
  zval = NULL,
  ...
)

tda_sd_plot3_lines(
  s,
  z,
  xlim = NULL,
  ylim = NULL,
  view = c(30, 30),
  width = 100,
  newpage = TRUE,
  symbol = NULL,
  size = NULL,
  zvar = NULL,
  zval = NULL,
  ...
)

tda_sd_plot3_polygons(
  s,
  z,
  xlim = NULL,
  ylim = NULL,
  view = c(30, 30),
  width = 100,
  newpage = TRUE,
  symbol = NULL,
  size = NULL,
  zvar = NULL,
  zval = NULL,
  ...
)

Arguments

s: a tda_spatial structure.
xlim, ylim: ranges of the x and y axes, taken from the structure when not given.
view: direction of the projection, as longitude and latitude in degrees; TDA's default is 30,30.
width: horizontal size of the plot in mm.
...: further options for the command.
p: a tda_sd_ps3 session.
cmd: the TDA command name.
zvar: an attribute carried in from the source file, used as each point's or polygon's height instead of a flat zval – for the polygon commands, each polygon is raised into a prism of that height rather than drawn flat. Name it as it appears in the object record – for a shapefile, a column of the .dbf.
symbol: marker symbol to draw at each point, as TDA's s=. It is named symbol rather than s because s is the spatial object.
size: marker size in mm.
zval: a single height for every point or polygon, when they do not have their own via zvar; TDA's default is 0.
z, zlim: the range of the z axis, as two numbers. Unlike x and y there is nothing in the spatial file to take it from, so it has no default.
newpage: start a new grid page.

Value

tda_sd_ps3() and the tda_sd_pl3_* functions return the session, with the command added. plot() on a session, and the one-shot functions, draw the plot and return the parsed drawing operations invisibly.

Details

A north-up view of geographic data (longitude/latitude, the way an ordinary map looks) is view = c(-90, 90), not TDA's own default of c(30, 30). This is a property of TDA's azimuth/elevation convention itself, not of any particular dataset, so it is the same for any longitude/latitude data.

Each of the three drawing commands only draws one kind of object, silently drawing nothing at all for any other kind: tda_sd_pl3_points draws points, tda_sd_pl3_lines draws lines, tda_sd_pl3_polygons draws polygons. A shapefile of counties, say, is polygons – points on it draws nothing, not because anything is wrong, but because it is looking for points that are not there. Check tda_sd_info first if it is not obvious which kind a structure holds.

tda_sd_plot3, tda_sd_plot3_lines and tda_sd_plot3_polygons are one-shot equivalents – set up a session, add one drawing command, plot it – kept for the simple case where nothing else needs adding to the same plot.

Examples

set.seed(1)
d <- data.frame(id = 1:8, x = runif(8), y = runif(8), z = runif(8))
s <- tda_spatial(d, attributes = "z")
pdf(NULL)

# composable form: build a session, add commands, plot it -- a title
# (via TDA's 3-D-aware text command, not the 2-D-only plabel) and an
# extra marker layered onto the same plot as the data
p <- tda_sd_ps3(s, zlim = c(0, 1))
p <- tda_sd_pl3_points(p, symbol = 1, size = 3)
p <- tda_pl_text3(p, "eight points", at = c(0.5, 0.5, 0.9))
plot(p)

# the one-shot form, for when nothing else needs adding
tda_sd_plot3(s, z = c(0, 1), symbol = 1, size = 3)

# plot3_lines wants line-type spatial data, not scattered points --
# a single connected line here, four vertices sharing one id
ln <- data.frame(id = 1, x = c(0, 0.3, 0.6, 1), y = c(0, 0.4, 0.5, 1),
                 z = c(0, 0.3, 0.6, 1))
sl <- tda_spatial(ln, type = 2, attributes = "z")
tda_sd_plot3_lines(sl, z = c(0, 1), symbol = 1)

# plot3_polygons draws flat polygons at a single height in the z range,
# or, given zvar, raises each one into a prism of that height -- h here
poly <- data.frame(id = 1, x = c(0, 2, 2, 0), y = c(0, 0, 2, 2),
                   h = c(2, 2, 2, 2))
sp <- tda_spatial(poly, type = 3, attributes = "h")
tda_sd_plot3_polygons(sp, z = c(0, 3), zvar = "h")

# a real shapefile, if one is available: sf's example data, North
# Carolina counties, in a proper north-up view, with city markers and
# labels layered on via TDA's 3-D-aware point/text commands
if (requireNamespace("sf", quietly = TRUE)) {
  nc <- tda_read_shapefile(system.file("shape/nc.shp", package = "sf"))
  cities <- data.frame(
    name = c("Raleigh", "Charlotte"),
    lon = c(-78.6382, -80.8431), lat = c(35.7796, 35.2271))

  pnc <- tda_sd_ps3(nc, zlim = c(0, 1), view = c(-90, 90))
  pnc <- tda_sd_pl3_polygons(pnc)
  # fs= is the marker/font size in mm, independent for each command --
  # the default marker size (2mm) reads as a large blob at this map's
  # own small default width (100mm), so it is turned down here, and
  # the default text size turned up, rather than using both defaults
  pnc <- tda_pl_points3(pnc, cities$lon, cities$lat, rep(0.5, 2),
                        symbol = 5, size = 0.8, lty = 0)
  for (i in seq_len(nrow(cities)))
    pnc <- tda_pl_text3(pnc, cities$name[i],
                        at = c(cities$lon[i] + 0.35, cities$lat[i], 0.5),
                        fs = 4)
  plot(pnc)
}
dev.off()
#> agg_record_1f9b4b78b557 
#>                       2

Usage

Arguments

Value

Details

See also

Examples