# Polygon Area (G Dataflow)

Calculates the signed area of a simple polygon.

## x

X-coordinates of the vertices of the polygon. You must specify at least three elements in this input.

## y

Y-coordinates of the vertices of the polygon. You must specify the same number of elements in y and x.

## error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

## signed area

Signed area of the polygon. signed area is positive if the vertices of the polygon are in counterclockwise order. Otherwise, signed area is negative.

## error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

## Algorithm for Calculating Polygon Area

A simple polygon is a polygon with no boundaries that cross each other.

The following equation defines the signed area of a simple polygon.

$A=\frac{1}{2}\sum _{i=0}^{n-1}\left({x}_{i}{y}_{i+1}-{x}_{i+1}{y}_{i}\right)$

where

• A is the signed area
• n is the number of vertices
• i is a reference to each vertex
• (x i , y i ) is the i th vertex
• (x n , y n ) = (x 0, y 0)

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application