在Python和PySpark中等效的R data.table滚动连接
有谁知道如何在PySpark中进行R data.table滚动连接?
借用Ben here的滚动连接的例子和很好的解释; sales<-data.table(saleID=c("S1","S2","S3","S4","S5"),saleDate=as.Date(c("2014-2-20","2014-5-1","2014-6-15","2014-7- 1","2014-12-31"))) commercials<-data.table(commercialID=c("C1","C2","C3","C4"),commercialDate=as.Date(c("2014-1-1","2014-4-1","2014-7-1","2014-9-15"))) setkey(sales,"saleDate") setkey(commercials,"commercialDate") sales[commercials,roll=TRUE] 结果是; saleDate saleID commercialID 1: 2014-01-01 NA C1 2: 2014-04-01 S1 C2 3: 2014-07-01 S4 C3 4: 2014-09-15 S4 C4 非常感谢您的帮助. 解决方法
滚动连接不是连接fillna
首先,滚动连接与连接和fillna不同!只有当连接的表的键(在data.table方面,即左表和右连接)在主表中具有等价物时才会出现这种情况. data.table滚动连接不需要这样. 据我所知,没有直接的等价物,我搜索了很长一段时间.它甚至有一个问题https://github.com/pandas-dev/pandas/issues/7546.但是: 大熊猫解决方案: 大熊猫有一个解决方案.我们假设您的右侧data??.table是表A,而您的左侧data??.table是表B. >按键对表A和B进行排序. 编程代码 #0. 'date' is the key for the rolling join. It does not have to be a date. A = pd.DataFrame.from_dict( {'date': pd.to_datetime(["2014-3-1","2014-6-1","2014-12-1"]),'value': ["a1","a2","a3","a4","a5"]}) B = pd.DataFrame.from_dict( {'date': pd.to_datetime(["2014-1-15","2014-3-15","2014-8-15","2014-11-15","2014-12-15"]),'value': ["b1","b2","b3","b4","b5","b6"]}) #1. Sort the table A and and B each by key. A = A.sort_values('date') B = B.sort_values('date') #2. Add a column tag to A which are all 0 and a column tag to B that are all 1. A['tag'] = 0 B['tag'] = 1 #3. Delete all columns except the key and tagfrom B (can be omitted,but it is clearer this way) and call the table B'. Keep B as an original - we are going to need it later. B_ = B[['date','tag']] # You need two [],because you get a series otherwise. #4. Concatenate A with B' to C and ignore the fact that the rows from B' has many NAs. C = pd.concat([A,B_]) #5. Sort C by key. C = C.sort_values('date') #6. Make a new cumsum column with C = C.assign(groupNr = np.cumsum(C.tag)) C = C.assign(groupNr = np.cumsum(C.tag)) #7. Using filtering (query) on tag get rid of all B'-rows. C = C[C.tag == 0] #8. Add a running counter column groupNr to the original B (integers from 0 to N-1 or from 1 to N,depending on whether you want forward or backward rolling join). B['groupNr'] = range(len(B)+1)[1:] # B's values are carried forward to A's values B['groupNr'] = range(len(B)) # B's values are carried backward to A's values #9. Join B with C on groupNr to D. D = C.set_index('groupNr').join(B.set_index('groupNr'),lsuffix='_A',rsuffix='_B') (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |