jarea {GEOmap}

Area of closed polygon.

Description

Returns area of polygon.

Usage

jarea(L)

Arguments

L

list with x,y components

Details

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

Value

Area in dimensions of x,y

Author(s)

Jonathan M. Lees<[e-mail]>

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 )