viewportTransform {grid} | R Documentation |

These functions define the transformation that will be applied
when a `grid.define()`

d group is `grid.use()`

d.

```
viewportTransform(group, shear=groupShear(), flip=groupFlip(), device=TRUE)
viewportTranslate(group, device=TRUE)
viewportScale(group, device=TRUE)
viewportRotate(group, device=TRUE)
defnTranslate(group, inverse=FALSE, device=TRUE)
defnScale(group, inverse=FALSE)
defnRotate(group, inverse=FALSE, device=TRUE)
useTranslate(inverse=FALSE, device=TRUE)
useScale(inverse=FALSE)
useRotate(inverse=FALSE, device=TRUE)
groupTranslate(dx=0, dy=0)
groupRotate(r=0, device=TRUE)
groupScale(sx=1, sy=1)
groupShear(sx=0, sy=0)
groupFlip(flipX=FALSE, flipY=FALSE)
```

`group` |
The group that is being transformed. |

`inverse` |
A logical indicating whether we want the forward or backward transformation. |

`shear` |
An affine transformation matrix that describes a shear transformation. |

`flip` |
An affine transformation matrix that describes a scaling inversion. |

`dx, dy` |
The translation to apply. |

`r` |
The rotation to apply. |

`sx, sy` |
The scaling (or shear) to apply. |

`flipX, flipY` |
Whether to negate the x-scaling or y-scaling (logical). |

`device` |
A logical indicating whether transformation should be relative to the device or relative to the current viewport. |

The `viewport*()`

functions are not called directly. They
are passed as the `transform`

argument to
`grid.use`

.

The `defn*()`

and `use*()`

functions are also not called
directly, but can be useful to create custom transformation
functions. For example, see the source code for
`viewportTransform`

.

The `group*()`

functions generate basic affine transformation
matrices and may also be useful to create custom transformation
functions. For example, the `groupShear()`

function can be
used to specify a shear transform to `viewportTransform()`

.

It is also possible to define any function that returns a 3x3 matrix
(as long as the last column contains 0, 0, and 1)
and use it as the `transform`

argument to
`grid.use`

, but the results will probably be
device-dependent, and may be *very* difficult
to predict. The function will be called with two arguments:
`group`

and `device`

.

An affine transformation matrix.

Paul Murrell

```
## NOTE: on devices without support for groups nothing will be drawn
grid.newpage()
## Define and use group in same viewport
pushViewport(viewport(width=.2, height=.2))
grid.define(circleGrob(gp=gpar(lwd=5)), name="circle")
grid.use("circle")
popViewport()
## Use group in viewport that is translated and scaled
pushViewport(viewport(x=.2, y=.2, width=.1, height=.1))
grid.use("circle")
popViewport()
## Use group in viewport that is translated and scaled
## BUT only make use of the translation
pushViewport(viewport(x=.2, y=.8, width=.1, height=.1))
grid.use("circle", transform=viewportTranslate)
popViewport()
## Use group in viewport that is translated and scaled
## unevenly (distorted)
pushViewport(viewport(x=.8, y=.7, width=.2, height=.4))
grid.use("circle")
popViewport()
```

[Package *grid* version 4.2.0 Index]