label_rule: Adds a label to the rule

In ropensci/pixelclasser: Classifies Image Pixels by Colour

Description

This function adds a label to the line that represents a rule on a plot created by plot_rgb_plane().

Usage

label_rule(rule, label = "", shift = c(0, 0), ...)

Arguments

rule	an object of class pixel_rule.
label	a string to label the line. It is attached at the coordinates of the start (first point) of the line.
shift	a numeric vector to set the displacement of the label from the start of the line. Expressed in graph units, defaults to c(0, 0).
...	additional graphical parameters passed to the underlying graphics::text() function.

Details

The function uses the information stored in the pixel_rule object to plot the label at the start of the line. The shift values, expressed in plot coordinates, are added to the coordinates of that point to place the label elsewhere. Note that ... can be used to pass values for the adj parameter to the underlying graphics::text() function, which also modifies the position of the label.

Use a character string understood by grDevices::col2rgb() to set the colour of the label.

Value

The function does not return any value.

See Also

plot_rgb_plane, define_rule, col2rgb, text

Examples

rule_01 <- define_rule("rule_01", "g", "b",
                       list(c(0.1, 0.8), c(0.40, 0.10)), "<")
plot_rgb_plane("g", "b")

# The rule is represented as a green line
plot_rule(rule_01, col = "green")

# And the label is added in three different positions by passing col and adj
# to the underlying function
label_rule(rule_01, label = expression('R'[1]*''), shift = c(0,0),
           col = 'black', adj = 1.5)
label_rule(rule_01, label = expression('R'[1]*''), shift = c(0.2, -0.4),
           col = 'blue', adj = 0)
label_rule(rule_01, label = expression('R'[1]*''), shift = c(0.3, -0.7),
           col = 'black', adj = -0.5)

ropensci/pixelclasser documentation built on Feb. 25, 2021, 2:08 p.m.