start_left: Does point C fall on the left side of the AB line?
In FluvialGeomorph/fluvgeo: A Package for Fluvial Geomorphic Analysis

start_left

R Documentation

Does point C fall on the left side of the AB line?

Description

Returns TRUE if the point C fall on the left side of the AB line. Orientation of the AB line determines the left and right side (i.e, starting at point A looking toward point B). Used to answer the question: Is point C on the left of the AB line?

Usage

start_left(a_x, a_y, b_x, b_y, c_x, c_y)

Arguments

`a_x`	numeric, Point A x coordinate
`a_y`	numeric, Point A y coordinate
`b_x`	numeric, Point B x coordinate
`b_y`	numeric, Point B y coordinate
`c_x`	numeric, Point C x coordinate
`c_y`	numeric, Point C y coordinate

Details

Uses the cross product method. Taken from: [SO](https://stackoverflow.com/questions/1560492/how-to-tell-whether-a-point-is-to-the-right-or-left-side-of-a-line)