function get() {
	/* eslint-disable no-invalid-this */
	var scale;
	if ( this._yScale === 'time' ) {
		scale = time()
			.domain( this.yDomain )
			.range( this.yRange );
	} else if ( this._yScale === 'linear' ) {
		scale = linear()
			.domain( this.yDomain )
			.range( this.yRange );
	}
	// TODO: other scales
	return scale;
}
Returns a scale function for mapping values to a coordinate along the y-axis.

@private
@returns {Function} scale function