// chebysheve outlier detection
// this function is used to detect the abnormal value among a set of data
// input:
// delta: a set of data
// flag: discribe which data is already known as outlier
// p: restrict level
// output:
// double[] door : byyond which the data may be considered as a outlier
// door[0]: the upperdoor
// door[1]: the lowerdoor
