# find_outmost_convexhull_points: Function which finds the outermost convex hull points in... In archetypal: Finds the Archetypal Analysis of a Data Frame

 find_outmost_convexhull_points R Documentation

## Function which finds the outermost convex hull points in order to be used as initial solution in archetypal analysis

### Description

Function which finds the outermost convex hull points in order to be used as initial solution in archetypal analysis

### Usage

``````find_outmost_convexhull_points(df, kappas)
``````

### Arguments

 `df` The data frame with dimensions n x d `kappas` The number of archetypes

### Details

This function uses the `chull` when d=2 (see [1], [2]) and the `convhulln` for d>2 (see [3]) cases.

### Value

A list with members:

1. outmost, the first kappas most frequent outermost points as rows of data frame

2. outmostall, all the outermost points that have been found as rows of data frame

3. outmostfrequency, a matrix with frequency and cumulative frequency for outermost rows

### References

[1] Eddy, W. F. (1977). A new convex hull algorithm for planar sets. ACM Transactions on Mathematical Software, 3, 398-403. doi: 10.1145/355759.355766.

[2] Eddy, W. F. (1977). Algorithm 523: CONVEX, A new convex hull algorithm for planar sets [Z]. ACM Transactions on Mathematical Software, 3, 411-412. doi: 10.1145/355759.355768.

[3] Barber, C.B., Dobkin, D.P., and Huhdanpaa, H.T., "The Quickhull algorithm for convex hulls" ACM Trans. on Mathematical Software, 22(4):469-483, Dec 1996, http://www.qhull.org

`find_furthestsum_points`, `find_outmost_projected_convexhull_points`,

`find_outmost_partitioned_convexhull_points` & `find_outmost_points`

### Examples

``````data("wd2") #2D demo
df = wd2
yy = find_outmost_convexhull_points(df, kappas = 3)
yy\$outmost #the rows of 3 outermost points
df[yy\$outmost,] #the 3 outermost points
yy\$outmostall #all outermost cH rows
yy\$outmostfrequency #their frequency
#
###
#
data("wd3") #3D demo
df = wd3
yy = find_outmost_convexhull_points(df, kappas = 4)
yy\$outmost #the rows of 4 outermost points
df[yy\$outmost,] #the 4 outermost points
yy\$outmostall #all outermost cH rows
yy\$outmostfrequency #their frequency
``````

archetypal documentation built on May 29, 2024, 8:46 a.m.