axTicks {graphics} | R Documentation |

## Compute Axis Tickmark Locations

### Description

Compute pretty tickmark locations, the same way as **R** does internally.
This is only non-trivial when **log** coordinates are active.
By default, gives the `at`

values which
`axis(side)`

would use.

### Usage

axTicks(side, axp = NULL, usr = NULL, log = NULL)

### Arguments

`side` |
integer in 1:4, as for `axis` . |

`axp` |
numeric vector of length three, defaulting to
`par("Zaxp")` where “Z” is “x” or
“y” depending on the `side` argument. |

`usr` |
numeric vector of length four, defaulting to
`par("usr")` giving horizontal (‘x’) and vertical
(‘y’) user coordinate limits. |

`log` |
logical indicating if log coordinates are active; defaults
to `par("Zlog")` where ‘Z’ is as for the
`axp` argument above. |

### Details

The `axp`

, `usr`

, and `log`

arguments must be consistent
as their default values (the `par(..)`

results) are. If you
specify all three (as non-NULL), the graphics environment is not used
at all. Note that the meaning of `axp`

alters very much when `log`

is `TRUE`

, see the documentation on `par(xaxp=.)`

.

`axTicks()`

can be regarded as an **R** implementation of the
C function `CreateAtVector()`

in ‘`..../src/main/plot.c`’
which is called by `axis(side,*)`

when no argument
`at`

is specified.

### Value

numeric vector of coordinate values at which axis tickmarks can be
drawn. By default, when only the first argument is specified,
these values should be identical to those that
`axis(side)`

would use or has used.

### See Also

`axis`

, `par`

. `pretty`

uses the same algorithm (but independently of the graphics
environment) and has more options. However it is not available for
`log = TRUE.`

### Examples

plot(1:7, 10*21:27)
axTicks(1)
axTicks(2)
stopifnot(identical(axTicks(1), axTicks(3)),
identical(axTicks(2), axTicks(4)))
## Show how axTicks() and axis() correspond :
op <- par(mfrow = c(3,1))
for(x in 9999*c(1,2,8)) {
plot(x,9, log = "x")
cat(formatC(par("xaxp"),wid=5),";",T <- axTicks(1),"\n")
rug(T, col="red")
}
par(op)

[Package

*graphics* version 2.2.1

Index]