R: Draw a text label or mathematical expression.

draw_label {cowplot}

R Documentation

Draw a text label or mathematical expression.

Description

This function can draw either a character string or mathematical expression at the given coordinates. It works both on top of ggdraw and directly with ggplot, depending on which coordinate system is desired (see examples).

Usage

draw_label(label, x = 0.5, y = 0.5, hjust = 0.5, vjust = 0.5,
  fontfamily = "", fontface = "plain", colour = "black", size = 14,
  angle = 0, lineheight = 0.9, alpha = 1)

Arguments

`label`	String or plotmath expression to be drawn.
`x`	The x location (origin) of the label.
`y`	The y location (origin) of the label.
`hjust`	Horizontal justification. Default = 0.5 (centered on x). 0 = flush-left at x, 1 = flush-right.
`vjust`	Vertical justification. Default = 0.5 (centered on y). 0 = baseline at y, 1 = ascender at y.
`fontfamily`	The font family
`fontface`	The font face ("plain", "bold", etc.)
`colour`	Text color
`size`	Point size of text
`angle`	Angle at which text is drawn
`lineheight`	Line height of text
`alpha`	The alpha value of the text

Details

By default, the x and y coordinates specify the center of the text box. Set hjust = 0, vjust = 0 to specify the lower left corner, and other values of hjust and vjust for any other relative location you want to specify.

Examples

# setup plot and a label (regression description)
p <- ggplot(mtcars, aes(mpg, disp)) + geom_line(color = "blue") + background_grid(minor = 'none')
c <- cor.test(mtcars$mpg, mtcars$disp, method = 'sp')
label <- substitute(paste("Spearman ", rho, " = ", estimate, ", P = ", pvalue),
                    list(estimate = signif(c$estimate, 2), pvalue = signif(c$p.value, 2)))

# Add label to plot, centered on {x,y} (in data coordinates)
p + draw_label(label, x = 20, y = 400)
# Add label to plot in data coordinates, flush-left at x, baseline at y.
p + draw_label(label, x = 20, y = 400, hjust = 0, vjust = 0)

# Add label to plot. Data coordinates, drawing rightward
# from x, with ascenders of text touching y.
p + draw_label(label, x = 20, y = 400, hjust = 0, vjust = 1)

# Add labels via ggdraw. Uses ggdraw coordinates.
# ggdraw coordinates default to xlim = c(0, 1), ylim = c(0, 1).
ggdraw(p) + draw_label("centered on 70% of x, 90% of y height", x = 0.7, y = 0.9)
labstr = "bottom left at {0%, 0%} of the SHEET, not the plot!"
p = ggdraw(p) + draw_label(labstr, x = 0, y = 0, hjust = 0, vjust = 0)
p = p + draw_label("top right at {1,1}", x = 1, y = 1, hjust = 1, vjust = 1)
p = p + draw_label("bottom left at {.4,.4}", x = 0.4, y = 0.4, hjust = 0, vjust = 0)
p + draw_label("centered on at {.5,.5}", x = 0.5, y = 0.5, hjust = 0.5, vjust = 0.5)