CFLib.org – Common Function Library Project

Description:
Purpose = Calcuate the area of an N sided irregular polygon. Formula = Area = 1/2 * ((x1+x2)(y1-y2)+(x2+x3)(y2-y3)+...+(xn+x1)(yn-y1)) Units = Units out are the same units as units in. Input = Array of X,Y points making up the polygon. Array must have at least three items.

Return Values:
Returns a number.

Example:

<cfset p = arrayNew(1)>
<cfset p[1] = structNew()>
<cfset p[1].x = 0>
<cfset p[1].y = 0>
<cfset p[2] = structNew()>
<cfset p[2].x = 5>
<cfset p[2].y = 0>
<cfset p[3] = structNew()>
<cfset p[3].x = 5>
<cfset p[3].y = 5>
<cfset p[4] = structNew()>
<cfset p[4].x = 0>
<cfset p[4].y = 5>

Parameters:

Full UDF Source:

/**
 * Calculates the area of an irregular N sided Polygon.
 * 
 * @param data      Array of structs (Required)
 * @return Returns a number. 
 * @author Tim Dudek (tim@igl.net) 
 * @version 1, January 26, 2004 
 */
function CalcPolygonArea(data) {
    var area = "0";
    var i = 1;

    // Check for valid Stucture with at least 3 records
    if(not isArray(data) or arrayLen(data) lte 2) return 0;
    
    data[arrayLen(data)+1] = structNew();
    data[arrayLen(data)].x = data[1].x;
    data[arrayLen(data)].y = data[1].y;
    

    // Loop through the structure performing the area calculation.
    // Formula = Area = 1/2 * ((x1+x2)(y1-y2)+(x2+x3)(y2-y3)+...+(xn+x1)(yn-y1))
    for(; i LT arrayLen(data) ; i=i+1) {
        area = area + ( data[i+1].x-data[i].x) * (data[i+1].y + data[i].y) / 2;
    }
    
    // Only return positive values.
    return abs(area);
}