Render labeled isolines

This function generates a grid grob that represents labeled isolines.

isolines_grob(
  lines,
  gp = gpar(),
  breaks = NULL,
  labels = NULL,
  margin = unit(c(1, 1, 1, 1), "pt"),
  label_col = NULL,
  label_alpha = NULL,
  label_placer = label_placer_minmax(),
  units = "npc"
)

Arguments

lines

Isolines, as produced by the isolines() function.

gp

Grid graphical parameters. Parameters applying to lines (such as col, lwd, lty, etc.) are recycled among the total number of lines drawn. Parameters applying only to labels (such as fontfamily, fontsize) are recycled among the specified breaks only. The two parameters col and alpha are also applied to labels, unless overridden (see label_col and label_alpha), but are matched to the corresponding lines.

breaks

Character vector specifying the isolines that should be labeled. If NULL, labels all isolines.

labels

Character vector specifying the labels for each break. If NULL, uses the breaks as labels. The number of labels provided must match the number of breaks provided.

margin

Unit object of length 4 specifying the top, right, bottom, and left margins around each text label. The same margins are applied to all labels.

label_col

Color applied to labels. Can be used to override the color provided in gp, in case labels and lines should have different colors.

label_alpha

Alpha applied to labels. Can be used to override the alpha value provided in gp, in case labels and lines should have different alpha values.

label_placer

Function that controls how labels are placed along the isolines. Uses label_placer_minmax() by default.

units

A character string specifying the units in which to interpret the isolines coordinates. Defaults to "npc".

See also

See isobands_grob() for drawing of isobands. See label_placer_minmax() for label placement strategies.

Examples

library(grid)

viridis_pal <- colorRampPalette(
  c("#440154", "#414487", "#2A788E", "#22A884", "#7AD151", "#FDE725"),
  space = "Lab"
)

x <- (1:ncol(volcano))/(ncol(volcano)+1)
y <- (nrow(volcano):1)/(nrow(volcano)+1)
lines <- isolines(x, y, volcano, 5*(19:38))
bands <- isobands(x, y, volcano, 5*(18:38), 5*(19:39))

b <- isobands_grob(
  bands,
  gp = gpar(col = NA, fill = viridis_pal(21), alpha = 0.4)
)
l <- isolines_grob(
  lines, breaks = 20*(5:10),
  gp = gpar(
    lwd = c(.3, 1, .3, .3)
  )
)

grid.newpage()
grid.draw(b)
grid.draw(l)