GEOmap (version 2.5-11)

jarea: Area of closed polygon.

Description

Returns area of polygon.

Usage

jarea(L)

Value

Area in dimensions of x,y

Arguments

L

list with x,y components

Author

Jonathan M. Lees<[e-mail]>

Details

If polygon is counter clockwise (CCW) area will be positive, else negative. If not sure, take absolute value of output.

Examples

set.seed(12)
X = runif(10, 1, 100)
    Y = runif(10, 1, 100)

    hc = chull(X, Y)
#### looks like chull returns points in clockwise
    L = list(x=X[hc] , y=Y[hc] )

  j1 = jarea(L )

#########  reverse order of polygon
jc = rev(hc)
    L = list(x=X[jc] , y=Y[jc] )
 j2 = jarea(L )