eyeRead (version 0.0.4)

convert: convert between units in eye-tracking

Description

The functions convert between visual degrees and centimeters, inches or pixels.

Usage

size2deg(x, dist)
px2deg(x, dist, res, screenW)
deg2size(x, dist)
deg2px(x, dist, res, screenW)

Arguments

x

The value to convert. This can be a single number or a numerical vector.

dist

The distance to the screen. See Details for the measurement unit.

res

A vector indicating the screen resolution in the horizontal direction (in pixels).

screenW

The width of the screen in the horizontal direction. See Details for the measurement unit.

Value

Returns a value or vector of values indicating the corresponding visual degrees.

Functions

• size2deg: converts from centimeters to visual degrees

• px2deg: converts from pixels to visual degrees

• deg2size: converts from visual degrees to centimeters

• deg2px: converts from visual degrees to pixels

Details

When converting from size to degrees (size2deg), the measurement unit of the distance to the screen (dist) should be consistent with the measurement unit of the size you are converting from (x. Namely if the size is in centimeters, then the distance should be to, and if the size is in inches, then the distance should be in inches.

When converting from pixels to degrees (px2deg), the measurement unit of the distance to the screen (dist) should be consistent with the measurement unit of the screen width (screen width). Namely if the size is in centimeters, then the screen width should be to, and if the size is in inches, then the screen width should be in inches.

Examples

# NOT RUN {
### these functions convert between units
  ## from size to degrees
  # for single values
  size2deg( x = 2, dist = 30 ) # 3.818304866
  
  # and multiple values
  size2deg( x = c( 2, 0.5, 7, 2, 20, 0.5 ),
            dist = c( 30, 30, 60, 15, 30, 15 ) )
   # 3.818304866, 0.954907555, 6.676941008, 7.628149669, 36.86989765, 
   # 1.909682508

## from pixels to degrees
  # for single values
  px2deg( x = 2, dist = 30, res = 1024, screenW = 32 ) # 0.119366164
  
  # and multiple values
  px2deg( x = c( 2, 8, 100 ), dist = 30, res = 1024, screenW = 32 )
    # 0.119366164, 0.477462066, 5.96292244

## from degrees to size
  # for single values
  deg2size( x = 2, dist = 30 ) # 1.047303896
  
  # and multiple values
  deg2size( x = c( 2, 8, 100 ), dist = 30 )
    # 1.047303896, 4.195608717, 71.50521556

## from degrees to pixels
  # for single values
  deg2px( x = 0.119366164, dist = 30, res = 1024, screenW = 32 ) # 2
  
  # and multiple values
   deg2px( x = c( 0.119366164, 0.477462066, 5.96292244 ), dist = 30,
           res = 1024, screenW = 32 )
     # 2, 8, 100

# }