# Change the unit of figure size

By default, R Markdown employs inch as a unit of figure size. You can change it by `hook_figure_unit`.

CAUTIONS

- This hook must not run twice in a document. Otherwise, you will face unexpected figure size.
- RStudio IDE do not detect the hook and treats `fig.width` and `fig.height` in inches.
- This hook sets `NULL` to the `fig.retina` chunk option.

# Basic usage

`hook_figure_unit()` changes to the unit of figure size to millimeters. Note that this hook will not change the default size.

    library(chunkhooks)
    hook_figure_unit()
    #> fig.retina is set NULL

    # fig.width=50, fig.height=50 (50mm * 50mm)
    plot(1)

## Other units

You may change default unit by the first argument, `unit`.

    hook_figure_unit("cm")

Choices are followings:

    measurements::conv_unit_options$length
    #>  [1] "angstrom"   "nm"         "um"         "mm"         "cm"
    #>  [6] "dm"         "m"          "km"         "inch"       "ft"
    #> [11] "foot"       "feet"       "yd"         "yard"       "fathom"
    #> [16] "mi"         "mile"       "naut_mi"    "au"         "light_yr"
    #> [21] "light_year" "parsec"     "point"