Common functions

reset_feedback()

Resets all feedback variables to their initial state.

Example

reset_feedback()

set_subject_nr(nr)

Sets the subject number and parity (even/ odd). This function is called automatically when an experiment is started, so you only need to call it yourself if you overwrite the subject number that was specified when the experiment was launched.

Example

set_subject_nr(1)
console.log('Subject nr = ' + vars.subject_nr)
console.log('Subject parity = ' + vars.subject_parity)

sometimes([p])

Returns true with a certain probability. (For more advanced randomization, use the random-ext package, which is available as random.)

Example

if (sometimes()) {
  console.log('Sometimes you win')
} else {
  console.log('Sometimes you lose')
}

xy_from_polar(rho, phi, [pole]) ⇒ Array.<Number>

Converts polar coordinates (distance, angle) to Cartesian coordinates (x, y).

Returns: Array.<Number> - An [x, y] array.

Example

// ECMA 5.1
var xy1 = xy_from_polar(100, 45)
var xy2 = xy_from_polar(100, -45)
var c = Canvas()
c.line({sx: xy1[0], sy: xy1[1], ex: -xy1[0], ey: -xy1[1]})
c.line({sx: xy2[0], sy: xy2[1], ex: -xy2[0], ey: -xy2[1]})
c.show()
// ECMA 6
let [x1, y1] = xy_from_polar(100, 45)
let [x2, y2] = xy_from_polar(100, -45)
let c = Canvas()
c.line({sx: x1, sy: y1, ex: -x1, ey: -y1})
c.line({sx: x2, sy: y2, ex: -x2, ey: -y2})
c.show()

xy_to_polar(x, y, [pole]) ⇒ Array.<Number>

Converts Cartesian coordinates (x, y) to polar coordinates (distance, angle).

Returns: Array.<Number> - An [rho, phi] array. Here, rho is the radial coordinate, also distance or eccentricity. phi is the angular coordinate in degrees (i.e. not radians), and reflects a counterclockwise rotation, where 0 is straight right.

Example

// ECMA 5.1 (browser + desktop)
var rho_phi = xy_to_polar(100, 100)
var rho = rho_phi[0]
var phi = rho_phi[1]
// ECMA 6 (browser only)
let [rho, phi] = xy_to_polar(100, 100)

xy_distance(x1, y1, x2, y2) ⇒ Number

Gives the distance between two points.

Returns: Number - The distance between the two points.

xy_circle(n, rho, [phi0], [pole]) ⇒ Array.<Array.<Number>>

Generates a list of points (x,y coordinates) in a circle. This can be used to draw stimuli in a circular arrangement.

Returns: Array.<Array.<Number>> - An array of [x,y] coordinate arrays.

Example

// Draw 8 rectangles around a central fixation dot
// ECMA 5.1 (browser + desktop)
var c = Canvas()
c.fixdot()
var points = xy_circle(8, 100)
for (var i in points) {
  var x = points[i][0]
  var y = points[i][1]
  c.rect({x: x - 10, y: y - 10, w: 20, h: 20})
}
c.show()
// ECMA 6 (browser only)
let c = Canvas()
c.fixdot()
for (let [x, y] of xy_circle(8, 100)) {
  c.rect({x: x - 10, y: y - 10, w: 20, h: 20})
}
c.show()

xy_grid(n, spacing, [pole]) ⇒ Array.<Array.<Number>>

Generates a list of points (x,y coordinates) in a grid. This can be used to draw stimuli in a grid arrangement.

Returns: Array.<Array.<Number>> - An array of [x,y] coordinate arrays.

Example

// Draw a 4x4 grid of rectangles
// ECMA 5 (desktop + browser)
var c = Canvas()
c.fixdot()
var points = xy_grid(4, 100)
for (var i in points) {
  var x = points[i][0]
  var y = points[i][1]
  c.rect({x: x - 10, y: y - 10, w: 20, h: 20})
}
c.show()
// ECMA 6 (browser only)
let c = Canvas()
c.fixdot()
for (let [x, y] of xy_grid(4, 100)) {
  c.rect({x: x-10, y: y-10, w: 20, h: 20})
}
c.show()

xy_random(n, width, height, [min_dist], [pole]) ⇒ Array.<Array.<Number>>

Generates a list of random points (x,y coordinates) with a minimum spacing between each pair of points. This function will throw an error when the coordinate list cannot be generated, typically because there are too many points, the min_dist is set too high, or the width or height are set too low.

Returns: Array.<Array.<Number>> - An array of [x,y] coordinate arrays.

Example

// Draw a 50 rectangles in a random grid
// ECMA 5 (desktop + browser)
var c = Canvas()
c.fixdot()
var points = xy_random(50, 500, 500, 40)
for (var i in points) {
  var x = points[i][0]
  var y = points[i][1]
  c.rect({x: x - 10, y: y - 10, w: 20, h: 20})
}
c.show()   
// ECMA 6 (browser only)
let c = Canvas()
c.fixdot()
for (let [x, y] of xy_random(50, 500, 500, 40)) {
  c.rect({x: x-10, y: y-10, w: 20, h: 20})
}
c.show()