motion-features

A monoclass library computing a customizable set of gestural descriptors, taking accelerometer and gyroscope sensors data as input.

List of available descriptors :

computed from accelerometer only :

• accIntensity : gesture intensity computed from the accelerometer
• kick : detects a hit gesture
• shake : amount of shakiness of a gesture

computed from gyroscope only :

• gyrIntensity : gesture intensity computed from the gyroscope
• spin : the global rotation speed
• still : tell if the sensors are still

computed from both accelerometer and gyroscope :

• freefall : tell if the sensors are falling

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API documentation :

MotionFeatures

Class computing the descriptors from accelerometer and gyroscope data.
es6 + browserify example :

import { MotionFeatures } from 'motion-features'; 
const mf = new MotionFeatures({ descriptors: ['accIntensity', 'kick'] });

// then, on each motion event :
mf.setAccelerometer(x, y, z);
mf.setGyroscope(alpha, beta, gamma);
mf.update(function(err, res) {
  if (err === null) {
    // do something with res
  }
});

Kind: global class

• MotionFeatures
  • new MotionFeatures(initObject)
  • .updateParams(params)
  • .setAccelerometer(x, y, z)
  • .setGyroscope(x, y, z)
  • .update(callback) ⇒ features

new MotionFeatures(initObject)

Param	Type	Description
initObject	Object	object containing an array of the required descriptors and some variables used to compute the descriptors that you might want to change (for example if the browser is chrome you might want to set gyrIsInDegrees to false because it's the case on some versions, or you might want to change some thresholds). See the code for more details.

motionFeatures.updateParams(params)

Update configuration parameters (except descriptors list)

Kind: instance method of MotionFeatures

Param	Type	Description
params	Object	a subset of the constructor's parameters

motionFeatures.setAccelerometer(x, y, z)

Sets the current accelerometer values.

Kind: instance method of MotionFeatures

Param	Type	Default	Description
x	Number		the accelerometer's x value
y	Number	0	the accelerometer's y value
z	Number	0	the accelerometer's z value

motionFeatures.setGyroscope(x, y, z)

Sets the current gyroscope values.

Kind: instance method of MotionFeatures

Param	Type	Default	Description
x	Number		the gyroscope's x value
y	Number	0	the gyroscope's y value
z	Number	0	the gyroscope's z value

motionFeatures.update(callback) ⇒ features

Triggers computation of the descriptors from the current sensor values and pass the results to a callback

Kind: instance method of MotionFeatures
Returns: features - features - Return these computed descriptors anyway

Param	Type	Default	Description
callback	featuresCallback		The callback handling the last computed descriptors

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accIntensity : Object

Intensity of the movement sensed by an accelerometer.

Kind: global typedef
Properties

Name	Type	Description
norm	Number	the global energy computed on all dimensions.
x	Number	the energy in the x (first) dimension.
y	Number	the energy in the y (second) dimension.
z	Number	the energy in the z (third) dimension.

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gyrIntensity : Object

Intensity of the movement sensed by a gyroscope.

Kind: global typedef
Properties

Name	Type	Description
norm	Number	the global energy computed on all dimensions.
x	Number	the energy in the x (first) dimension.
y	Number	the energy in the y (second) dimension.
z	Number	the energy in the z (third) dimension.

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freefall : Object

Information about the free falling state of the sensor.

Kind: global typedef
Properties

Name	Type	Description
accNorm	Number	the norm of the acceleration.
falling	Boolean	true if the sensor is free falling, false otherwise.
duration	Number	the duration of the free falling since its beginning.

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kick : Object

Impulse / hit movement detection information.

Kind: global typedef
Properties

Name	Type	Description
intensity	Number	the current intensity of the "kick" gesture.
kicking	Boolean	true if a "kick" gesture is being detected, false otherwise.

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shake : Object

Shake movement detection information.

Kind: global typedef
Properties

Name	Type	Description
shaking	Number	the current amount of "shakiness".

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spin : Object

Information about the spinning state of the sensor.

Kind: global typedef
Properties

Name	Type	Description
spinning	Boolean	true if the sensor is spinning, false otherwise.
duration	Number	the duration of the spinning since its beginning.
gyrNorm	Number	the norm of the rotation speed.

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still : Object

Information about the stillness of the sensor.

Kind: global typedef
Properties

Name	Type	Description
still	Boolean	true if the sensor is still, false otherwise.
slide	Number	the original value thresholded to determine stillness.

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features : Object

Computed features.

Kind: global typedef
Properties

Name	Type	Description
accIntensity	accIntensity	Intensity of the movement sensed by an accelerometer.
gyrIntensity	gyrIntensity	Intensity of the movement sensed by a gyroscope.
freefall	freefall	Information about the free falling state of the sensor.
kick	kick	Impulse / hit movement detection information.
shake	shake	Shake movement detection information.
spin	spin	Information about the spinning state of the sensor.
still	still	Information about the stillness of the sensor.

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featuresCallback : function

Callback handling the features.

Kind: global typedef

Param	Type	Description
err	String	Description of a potential error.
res	features	Object holding the feature values.

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