## Plotting Dimensions of Character Strings and Math Expressions

## Usage

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

## Arguments

`s` | character vector or `expression`s whose string widths in plotting units are to be determined.
`units` | character indicating in which units `s` is measured; must be one of `"user"`, `"inches"`, `"figure"` .
`cex` | character expansion to which is applies. Per default, the current `par("cex")` is used.

## 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")`.

## Value

integer vector with the same length as `s`, giving the width for each `s[i]`.

## See Also

`text`, `nchar`

## Examples

    str.ex <- c("W","w","I",".","WwI.")
    op <- par(pty='s'); plot(1:100,1:100); par('usr')
    sw <- strwidth(str.ex); sw
    sum(sw[1:4] == sw[5])#- since the last string contains the others
    sw / strwidth(str.ex, cex = .5)
    # between 1.5 and 4.2 (!),  font dependent

    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")
    table(shL)# all have same heights ..
    mean(shL) / par("cin")[2] # should be 1 (exactly?)

    swL <- strwidth(all.lett)
    swL <- 3 * swL / min(swL)
    all(swL == round(swL))#- TRUE !
    swL <- as.integer(swL)
    n.classes <- length(tL <- table(swL)); tL
    iL <- order(swL)
    structure(swL[iL], names = all.lett[iL])
    lett.classes <- structure(vector("list", n.classes), names= names(tL))
    for(i in 1:n.classes)
      lett.classes[[i]] <- all.lett[swL == as.numeric(names(tL)[i])]
    lett.classes

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

    rm(sumex); par(op)#- reset to previous setting

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