grid.convert | R Documentation |
These functions take a unit object and convert it to an equivalent unit object in a different coordinate system.
convertX(x, unitTo, valueOnly = FALSE) convertY(x, unitTo, valueOnly = FALSE) convertWidth(x, unitTo, valueOnly = FALSE) convertHeight(x, unitTo, valueOnly = FALSE) convertUnit(x, unitTo, axisFrom = "x", typeFrom = "location", axisTo = axisFrom, typeTo = typeFrom, valueOnly = FALSE)
x |
A unit object. |
unitTo |
The coordinate system to convert the unit to.
See the |
axisFrom |
Either |
typeFrom |
Either |
axisTo |
Same as |
typeTo |
Same as |
valueOnly |
A logical indicating. If |
The convertUnit
function allows for general-purpose
conversions. The other four functions are just more convenient
front-ends to it for the most common conversions.
The conversions occur within the current viewport.
It is not currently possible to convert to all valid coordinate systems (e.g., "strwidth" or "grobwidth"). I'm not sure if all of these are impossible, they just seem implausible at this stage.
In normal usage of grid, these functions should not be necessary.
If you want to express a location or dimension in inches rather
than user coordinates then you should simply do something like
unit(1, "inches")
rather than something like
unit(0.134, "native")
.
In some cases, however, it is necessary for the user to perform calculations on a unit value and this function becomes necessary. In such cases, please take note of the warning below.
A unit object in the specified coordinate system
(unless valueOnly
is TRUE
in which case
the returned value is a numeric).
The conversion is only valid for the current device size.
If the device is resized then at least some conversions will
become invalid. For example, suppose that I create a unit
object as follows: oneinch <- convertUnit(unit(1, "inches"),
"native")
. Now if I resize the device, the unit object in
oneinch no longer corresponds to a physical length of 1 inch.
Paul Murrell
unit
## A tautology convertX(unit(1, "inches"), "inches") ## The physical units convertX(unit(2.54, "cm"), "inches") convertX(unit(25.4, "mm"), "inches") convertX(unit(72.27, "points"), "inches") convertX(unit(1/12*72.27, "picas"), "inches") convertX(unit(72, "bigpts"), "inches") convertX(unit(1157/1238*72.27, "dida"), "inches") convertX(unit(1/12*1157/1238*72.27, "cicero"), "inches") convertX(unit(65536*72.27, "scaledpts"), "inches") convertX(unit(1/2.54, "inches"), "cm") convertX(unit(1/25.4, "inches"), "mm") convertX(unit(1/72.27, "inches"), "points") convertX(unit(1/(1/12*72.27), "inches"), "picas") convertX(unit(1/72, "inches"), "bigpts") convertX(unit(1/(1157/1238*72.27), "inches"), "dida") convertX(unit(1/(1/12*1157/1238*72.27), "inches"), "cicero") convertX(unit(1/(65536*72.27), "inches"), "scaledpts") pushViewport(viewport(width=unit(1, "inches"), height=unit(2, "inches"), xscale=c(0, 1), yscale=c(1, 3))) ## Location versus dimension convertY(unit(2, "native"), "inches") convertHeight(unit(2, "native"), "inches") ## From "x" to "y" (the conversion is via "inches") convertUnit(unit(1, "native"), "native", axisFrom="x", axisTo="y") ## Convert several values at once convertX(unit(c(0.5, 2.54), c("npc", "cm")), c("inches", "native")) popViewport() ## Convert a complex unit convertX(unit(1, "strwidth", "Hello"), "native")
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