R: Calculate Metric Information for Text

calcStringMetric {grid} | R Documentation

## Calculate Metric Information for Text

### Description

This function returns the ascent, descent, and width metric information for a character or expression vector.

### Usage

    calcStringMetric(text)

### Arguments

`text` | A character or expression vector.

### Value

A list with three numeric components named ascent, descent, and width. All values are in inches.

### WARNING

The metric information from this function is based on the font settings that are in effect when this function is called. It will not necessarily correspond to the metric information of any text that is drawn on the page.

### Author(s)

Paul Murrell

### See Also

`stringAscent`, `stringDescent`, `grobAscent`, and `grobDescent`.

### Examples

    grid.newpage()
    grid.segments(.01, .5, .99, .5, gp=gpar(col="grey"))
    metrics <- calcStringMetric(letters)
    grid.rect(x=1:26/27,
              width=unit(metrics$width, "inches"),
              height=unit(metrics$ascent, "inches"),
              just="bottom",
              gp=gpar(col="red"))
    grid.rect(x=1:26/27,
              width=unit(metrics$width, "inches"),
              height=unit(metrics$descent, "inches"),
              just="top",
              gp=gpar(col="red"))
    grid.text(letters, x=1:26/27, just="bottom")

    test <- function(x) {
        grid.text(x, just="bottom")
        metric <- calcStringMetric(x)
        if (is.character(x)) {
            grid.rect(width=unit(metric$width, "inches"),
                      height=unit(metric$ascent, "inches"),
                      just="bottom",
                      gp=gpar(col=rgb(1,0,0,.5)))
            grid.rect(width=unit(metric$width, "inches"),
                      height=unit(metric$descent, "inches"),
                      just="top",
                      gp=gpar(col=rgb(1,0,0,.5)))
        } else {
            grid.rect(width=unit(metric$width, "inches"),
                      y=unit(.5, "npc") + unit(metric[2], "inches"),
                      height=unit(metric$ascent, "inches"),
                      just="bottom",
                      gp=gpar(col=rgb(1,0,0,.5)))
            grid.rect(width=unit(metric$width, "inches"),
                      height=unit(metric$descent, "inches"),
                      just="bottom",
                      gp=gpar(col=rgb(1,0,0,.5)))
        }
    }

    tests <- list("t",
                  "test",
                  "testy",
                  "test\ntwo",
                  expression(x),
                  expression(y),
                  expression(x + y),
                  expression(a + b),
                  expression(atop(x + y, 2)))

    grid.newpage()
    nrowcol <- n2mfrow(length(tests))
    pushViewport(viewport(layout=grid.layout(nrowcol[1], nrowcol[2]),
                          gp=gpar(cex=5, lwd=.5)))
    for (i in 1:length(tests)) {
        col <- (i - 1) %% nrowcol[2] + 1
        row <- (i - 1) %/% nrowcol[2] + 1
        pushViewport(viewport(layout.pos.row=row, layout.pos.col=col))
        test(tests[[i]])
        popViewport()
    }

[Package grid version 3.1.2 Index]