understanding-论文

understanding temporal and spatial travel paterns of individual passengers by mining smart card data

Question1:what is the temporal acess pattern?

Question2:what is the spatio access pattern?

Question3:is there any relationship between the temporal and spatio pattern?

Question4:is this passenger's paterns normal or special?

(如何能既能表现temporal和spatio，刷卡人的每次出行，时间和空间不能分家，仅时间不可以，仅空间也不可以，因此如何把他们俩个同时表示出来才可以)

benifit:

• policy evaluation
• anomaly detection（beggar:specail passengers）
• social networking（a scalable processing:connecting the passengers with similar public transportation patterns）

contribution:

• a systematic approach :extract temporal and spatial features,uses spatio-temporal analyse to perform abnoramal detection.
• an in-depth analysis and explanations for different groups

Morency 的三篇论文与其相似，已下载

Dataset: a month,21 weekdays,metro or bus transactions

Data preprocessing:

1. find all trips belongs to one passenger
2. filter out the passengers that rarely take metro.make a picture to show the distribution of the number of passengers according to the number of active days:有80%的人活动工作日天数少于7，20%的最活跃的人占有68% 的交易。研究那些很少出行的人没有意义，因此将工作日天数少于6的人去掉

 Temporal features extraction:  n维数据来描述时间属性

• n值不能太大也不能太小
• the central idea of temporal feature extraction is to divide time into sequential and overlapped slots.
• 选择这个的原因，第一：non-overlapped slots即不重叠的时间序列很难表示一些trips；第二：很少有trips超过三个小时，因此把时间长度定位3小时，8:00-10:59；9:00-11:59等
• 三步骤提取时空属性

Spatial features extract:  

• OD矩阵，按OD对的频率下降排列，将空间属性的值设为4

anomaly features extract：

• 用时多于相同的OD用时  概率W ；起始点与终点相同  概率P ；
• 需要找出这两种异常经常发生的人

Temporal analysis:

• Clustering:k-means 将按时间属性将乘客分成四类：

1. TGrp1:one dominant travel slot
2. TGrp2:two dominant travel slot
3. TGrp3:one relatively high dominant travel slot and one general travel slot
4. TGrp4:no significant diference

• 分析一番，将公交聚类，BTGrp1-4
• 将TGrp与BTGrp 结合起来分析，分析乘客的行为

Spatial analysis:

• k-means聚类方法将其分成四类

1. SGrp1:only one frequently accessed OD-pair
2. SGrp2:two frequently accessed OD -pairs
3. SGrp3:one relatively frequnetly accessed OD-pair and one general accessed OD-pair
4. SGrp4:no remarkable frequently accessed OD-pair

• SGrp与TGrp的关系：使用条件概率，发现概率很大
• 解释为什么有些人choose metro in a single trip and choose bus in another trip ,instead of metro in round trips.

Anomaly analysis:

• W：the radio of abnomal travel time trips
• P:the radio of abnomal OD pairs of a passengers
• 将概率W与P为40%一下的去掉，WP二维散点表，得到几类异常