end FUNCTION quantiles() 
FUNCTION: quantile( vector, percent )
Finds a quantile value.

@private
@param {array} vector - 1d array
@param {number} percent - quantile percent [0,1]
@returns {number} quantile value
function quantile( vector, percent ) {
		var numValues = vector.length,
			id, value;

		// Calculate the vector index marking the quantile:
		id = ( numValues * percent ) - 1;

		// Is the index an integer?
		if ( id === parseInt( id, 10 ) ) {
			// Value is the average between the value at id and id+1:
			value = ( vector[ id ] + vector[ id+1 ] ) / 2.0;
		} else {
			// Round up to the next index:
			id = Math.ceil( id );
			value = vector[ id ];
		}
		return value;
	}