R: Functions for using an imported coordinate system

Coordinate Conversion Functions {gridSVG} | R Documentation

## Functions for using an imported coordinate system

### Description

These functions convert between different units. The conversion occurs within viewports unknown to `grid`, but imported to R via `gridSVGCoords`.

### Usage

    viewportConvertX(vpname, x, from, to = "svg")
    viewportConvertY(vpname, x, from, to = "svg")
    viewportConvertPos(vpname, x, y, from, to = "svg")
    viewportConvertWidth(vpname, x, from, to)
    viewportConvertHeight(vpname, x, from, to)
    viewportConvertDim(vpname, w, h, from, to)

### Arguments

`vpname` | The name of the viewport that the unit belongs within.
`x, y, w, h` | The size of the unit in `from` units.
`from` | The type of unit that `x` is.
`to` | The unit that `x` is being converted to.

### Details

Although `grid` has conversion functions available, it only converts units relative to the current viewport. After writing out to SVG, we no longer have actual grid viewports to convert units within.

These functions are designed so that once coordinate information is loaded into `gridSVG` via `gridSVGCoords`, we can translate units within each of these viewports. Note: this requires that a `gridSVG` plot has had viewport information exported.

These functions can be used in much the same way as `grid`'s unit conversion functions, the only difference being that we have a new unit, `svg`, which represents the size of a unit in SVG pixels.

The `viewportConvertPos()` and `viewportConvertDim()` functions are for use with a viewport that has a non-zero rotation (both `viewportConvertX()` and `viewportConvertY()` will fail in that situation and `viewportConvertWidth()` and `viewportConvertHeight()` will give a not very useful answer).

### Value

A numeric vector containing a single value, the value of the new unit, or a list with components `x` and `y` for `viewportConvertPos()`, or a list with components `w` and `h` for `viewportConvertDim()`.

In the case of the `viewportConvertX` and `viewportConvertY` functions, we always return a value that is in terms of SVG pixels.

### Author(s)

Simon Potter

[Package gridSVG version 1.6-0 Index]