RFI | R Documentation |

A function that calculates relief index following Boyer (2008) Relief index of second mandibular molars is a correlate of diet among prosimian primates and other mammals. J Hum Evol 55:1118-1137 doi: 10.1016/j.jhevol.2008.08.002

RFI(plyFile, alpha = 0.075, findAlpha = FALSE)

`plyFile` |
An object of classes 'mesh3d' and 'shape3d' |

`alpha` |
Step size for calculating the outline. See details. |

`findAlpha` |
Logical indicating that alpha will be auto-calculated. See details. |

The function requires an object created by reading in a ply file utilizing
either the `vcgPlyRead`

function.

Relief index is calculated by the ratio of three-dimensional surface area to two dimensional area on meshes that represent specimen surfaces and have already been pre-smoothed in a 3D data editing program. Surface alignment will have a large effect on 2D area calculation and must be performed prior to creating and reading in the ply file. The mesh must be oriented such that the occlusal plane is parallel to the X- and Y-axes and perpendicular to the Z-axis (i.e., tooth cusps pointing towards +Z).

The `alpha`

parameter traces the outline of the 2D footprint. An `alpha`

that is
too low will result in a tracing error (returning an `"Alpha adjustment required"`

message), while an `alpha`

value that is too high may result in an overestimate
of the 2D footprint area by failing to take into account infoldings. The user is
encouraged to carefully review results using the `RFI3d`

or
`Check2D`

functions.

Alternatively, the `findAlpha`

argument can be used to compute an ideal `alpha`

value for a particular PLY file for use in the RFI calculation. This is defined as the
lowest value (to the nearest thousandth) returning no error or warning messages.
This feature ensures accuracy, but may increase computing time significantly,
depending on the number of `alpha`

values tested. Unfortunately, there is no way
to guess an appropriate `alpha`

value a priori. After 100 unsuccessful attempts to
find an appropriate `alpha`

, the function will terminate.

The `alpha`

value used in the calculation (whether chosen by the user or auto-
computed with `findAlpha`

) is returned in the analysis results.

RFI_output <- RFI(Tooth, alpha=0.5, findAlpha = FALSE) summary(RFI_output)

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