# computeArea: Compute area enclosed within an irregular polygon In Morpho: Calculations and Visualisations Related to Geometric Morphometrics

 computeArea R Documentation

## Compute area enclosed within an irregular polygon

### Description

Compute area enclosed within an irregular polygon - i.e. defined by curves

### Usage

```computeArea(x)
```

### Arguments

 `x` k x 2 or k x 3 matrix containing ordered coordinates forming the boundary of the area. For 3D-cases, the area should be closed to a 2D surface (see details below).

### Details

For 3D coordinates, a PCA is computed and only the first two PCs are used to compute the area. This is a projection of the coordinates onto a 2D plane spanned by those PCs.

### Value

returns a list containing

 `area` size of the enclosed area `xpro2D` projected coordinates of x in the 2D plane. `poly` object of class `sp` as defined by the `sp` package. `xpro3D` For 3D-cases, this contains the projected coordinates of x rotated back into the original coordinate system

### Note

in case custom planes are preferred, the data can first be projected onto such a custom defined plane via `points2plane` first.

### Examples

```require(shapes)
require(sf)
myarea <- computeArea(gorf.dat[c(1,6:8,2:5),,1])
myarea\$area
plot(myarea\$poly)

## 3D example
data(boneData)
myarea3D <- computeArea(boneLM[c(4,2,3,7,5,6,8),,1])
plot(myarea3D\$poly)
cent <- colMeans(myarea3D\$xpro2D)
text(cent[1],cent[2],labels=paste0("Area=",round(myarea3D\$area,digits=2)))
```

Morpho documentation built on Feb. 16, 2023, 10:51 p.m.