# subtendedAngle: Subtended Angle In eyetracking: Eyetracking Helper Functions

## Description

Takes two screen coordinates and returns the angle (in degrees) subtended by those two points.

## Usage

 `1` ```subtendedAngle(x1, y1, x2, y2, viewerDistance = 58.74, viewerHeight = 4.55, resolutionX = 1280, resolutionY = 1024, screenWidth = 33.97, screenHeight = 27.31) ```

## Arguments

 `x1` The x coordinate of the first point on a screen `y1` The y coordinate of the first point on a screen `x2` The x coordinate of the second point on a screen `y2` The y coordinate of the second point on a screen `viewerDistance` Perpendicular distance from the viewer to the screen (cm) `viewerHeight` Vertical height of the viewer above screen center (cm) `resolutionX` The x resolution of the monitor (pixels) `resolutionY` The y resolution of the monitor (pixels) `screenWidth` The physical screen width (cm) `screenHeight` The physical screen height (cm)

## Value

The angle (in degrees) subtended by two points

Ryan M. Hope

## Examples

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15``` ```function( x1, y1, x2, y2, viewerDistance=58.74, viewerHeight=4.55, resolutionX=1280, resolutionY=1024, screenWidth=33.97, screenHeight=27.31 ) { d1 <- distance2point(x1, y1, viewerDistance, viewerHeight, resolutionX, resolutionY, screenWidth, screenHeight) d2 <- distance2point(x2, y2, viewerDistance, viewerHeight, resolutionX, resolutionY, screenWidth, screenHeight) dX <- screenWidth * ( x2 - x1 ) / resolutionX dY <- screenWidth * ( y2 - y1 ) / resolutionY screenDistance <- sqrt( dX^2 + dY^2 ) angleRadians <- acos( ( d1^2 + d2^2 - screenDistance^2 ) / ( 2 * d1 * d2 ) ) angleRadians / ( 2 * pi ) * 360 } ```

eyetracking documentation built on May 2, 2019, 11:06 a.m.