# xtractlip: Extract Convex Hull Ellipse from fry In geophys: Geophysics, Continuum Mechanics, Gravity Modeling

## Description

Extract Convex Hull Ellipse from fry-diagram

## Usage

 `1` ```xtractlip(AF) ```

## Arguments

 `AF` x-y List out put of plotfry

## Details

To get closest points to center, program cycles around in a circular manner pulling out the closest points. These points are used to estimate the chull ellipse.

## Value

List: see output of ellipsoidhull: an object of class '"ellipsoid"', basically a 'list' with several components

## Author(s)

Jonathan M. Lees<[email protected]>

## References

Fry, N., (1979) <http://dx.doi.org/10.1016/0040-1951(79)90135-5> Random point distributions and strain measurement in rocks Tectonophysics, 60:89-105.

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17``` ```RDAT = randFRY(400, LIM=c(0,0, 200, 200) , rlen=5 ) length(RDAT\$x) plot(RDAT\$x, RDAT\$y, asp=1, pch=".", cex=2) flag = sqrt( (RDAT\$x-mean(RDAT\$x))^2 + (RDAT\$y-mean(RDAT\$y))^2)<75 DAT = list(x=RDAT\$x[flag], y=RDAT\$y[flag]) x = DAT\$x y = DAT\$y plot(x,y, asp=1, pch=21, col='red', bg='gold', ann=FALSE, axes=FALSE) FF = dofry(DAT\$x, DAT\$y ) AF = plotfry(FF, dis=30) Z = xtractlip(AF) lines(cluster::predict.ellipsoid(Z\$hull), col='red') ```