terra (version 1.9-25)

legend_cont: Add a continuous legend

Description

Add a continuous (color gradient) legend to an existing plot. This can be used with any base plot, not just plot,SpatRaster,numeric-method. The legend is drawn as a color bar with tick marks and labels.

Usage

legend_cont(x="right", y=NULL, legend, col,
    size=NULL, title=NULL, at=NULL, digits=NULL, ...)

Value

Invisible list with the legend parameters (can be used for further customization).

Arguments

x

character or numeric. Position of the legend. Keywords: "right", "left", "top", "bottom", "topright", "bottomright". Or a numeric x-coordinate (see y)

y

numeric. Optional y-coordinate(s) for the legend position, used when x is numeric

legend

SpatRaster or numeric vector. Used to determine the value range of the legend. If a SpatRaster, the range is taken from minmax. If numeric (e.g. c(min, max)), the range of the values is used

col

character. Vector of colors for the gradient. If missing, the default palette is used (map.pal("viridis", 100))

size

numeric. One or two values to control the size of the legend bar. The first value scales the length (0 to 1), the second scales the width

title

character. Title to display above or beside the legend bar

at

numeric. Specific values at which to place tick marks. If NULL (the default), ticks are placed automatically with pretty

digits

non-negative integer. Number of decimal places for tick labels. If NULL (the default) an appropriate number is computed from the range

...

Additional legend parameters: bg (background color behind the legend, e.g. "white"), cex, horiz, reverse, labels, tic (or tick), tic.col, tic.lwd, tic.box.col, and others (see the plg argument in plot,SpatRaster,numeric-method for details)

See Also

add_legend, add_box, plot,SpatRaster,numeric-method

Examples

# with a SpatRaster
r <- rast(ncols=40, nrows=40, xmin=0, xmax=1, ymin=0, ymax=1, vals=runif(1600))
plot(r, legend=FALSE, mar=c(3.1, 3.1, 2.1, 7.1))
legend_cont("right", legend=r)

# horizontal
plot(r, legend=FALSE, mar=c(6.1, 3.1, 2.1, 2.1))
legend_cont("bottom", legend=r, horiz=TRUE, title="values")

# on the map 
plot(r, legend=FALSE, alpha=0.1)
legend_cont(0.1, legend=r)
legend_cont(0.3, c(0.5, 0.9), legend=r, bg="white")
legend_cont(c(0.4, 0.8), 0.2, horiz=TRUE, legend=r, bg="white")


# with a numeric range and custom colors
cols <- heat.colors(100)
vals <- seq(5,95,10)
par(mar=c(3.1, 3.1, 2.1, 7.1))
plot(1:10, col=cols[vals], cex=2, pch=20)
legend_cont("right", legend=c(1, 100), col=cols)