strwidth {graphics}

R Documentation

Plotting Dimensions of Character Strings and Math Expressions

Description

These functions compute the width or height, respectively, of the given strings or mathematical expressions s[i] on the current plotting device in user coordinates, inches or as fraction of the figure width par("fin").

Usage

strwidth(s, units = "user", cex = NULL, font = NULL, vfont = NULL, ...)
strheight(s, units = "user", cex = NULL, font = NULL, vfont = NULL, ...)

Arguments

s	a character or expression vector whose dimensions are to be determined. Other objects are coerced by as.graphicsAnnot.
units	character indicating in which units s is measured; should be one of "user", "inches", "figure"; partial matching is performed.
cex	numeric character expansion factor; multiplied by par("cex") yields the final character size; the default NULL is equivalent to 1.
font, vfont, ...	additional information about the font, possibly including the graphics parameter "family": see text.

Details

Where an element of s is a multi-line string (that is, contains newlines \n), the width and height are of an enclosing rectangle of the string as plotted by text. The inter-line spacing is controlled by cex, par("lheight") and the ‘point size’ (but not the actual font in use).

Measurements in "user" units (the default) are only available after plot.new has been called – otherwise an error is thrown.

Value

Numeric vector with the same length as s, giving the width or height for each s[i]. NA strings are given width and height 0 (as they are not plotted).

See Also

text, nchar

Examples

str.ex <- c("W","w","I",".","WwI.")
op <- par(pty='s'); plot(1:100,1:100, type="n")
sw <- strwidth(str.ex); sw
all.equal(sum(sw[1:4]), sw[5])
#- since the last string contains the others

sw.i <- strwidth(str.ex, "inches"); 25.4 * sw.i # width in [mm]
unique(sw / sw.i)
# constant factor: 1 value
mean(sw.i / strwidth(str.ex, "fig")) / par('fin')[1] # = 1: are the same

## See how letters fall in classes
##  -- depending on graphics device and font!
all.lett <- c(letters, LETTERS)
shL <- strheight(all.lett, units = "inches") * 72 # 'big points'
table(shL) # all have same heights ...
mean(shL)/par("cin")[2] # around 0.6

(swL <- strwidth(all.lett, units="inches") * 72) # 'big points'
split(all.lett, factor(round(swL, 2)))

sumex <- expression(sum(x[i], i=1,n), e^{i * pi} == -1)
strwidth(sumex)
strheight(sumex)

par(op)#- reset to previous setting

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